Under a mechanism that is integrated in the UK merger control regime, as laid out in the 2002 Enterprise Act, the government can intervene to review a transaction from the perspective of public interest considerations, including national security but also media plurality and financial stability. Where an investigation finds that the transaction operates against the stated public interest consideration, remedial measures may be taken, including blocking the transaction or allowing it to proceed subject to certain conditions. Under the review mechanism, a merger or acquisition can be reviewed if the target company's turnover exceeds £70 million, or if the transaction results in the creation or enhancement of a "share of supply" of goods and services of at least 25% in the UK or in a substantial part of the UK. In 2018, the Act was amended to lower the turnover test threshold to £1 million with regard to "relevant enterprises". Relevant enterprises are involved in activities connected with the development or production of items for military or military and civilian use (‘dual use’); the design and maintenance of aspects of computing hardware; or the development and production of quantum technology. The share of supply test was likewise amended to also cover situations where the acquisition target already supplies 25% of the UK market in its sector.

The provisions of the Enterprise Act are of general application and not specific to foreign investors.
"23 Relevant merger situations
(1)For the purposes of this Part, a relevant merger situation has been created if—
(a)two or more enterprises have ceased to be distinct enterprises at a time or in circumstances falling within section 24; and
(b)the value of the turnover in the United Kingdom of the enterprise being taken over exceeds—
[(i)£1 million, if in the course of the enterprises ceasing to be distinct, a person or group of persons has brought a relevant enterprise (see section 23A) under the ownership or control of the person or group; or
(ii)£70 million, in any other case.]
(2)For the purposes of this Part, a relevant merger situation has also been created if—
(a)two or more enterprises have ceased to be distinct enterprises at a time or in circumstances falling within section 24; and
[(b)the share of supply test is met.]
[(2A)The share of supply test is met if—
(a)as a result of the enterprises ceasing to be distinct enterprises, one or both of the conditions mentioned in subsections (3) and (4) below prevails or prevails to a greater extent; or
(b)in the course of the enterprises ceasing to be distinct a person or group of persons has brought a relevant enterprise under the ownership or control of the person or group and one or both of the conditions mentioned in subsections (4A) and (4B) below was satisfied in relation to the relevant enterprise before it ceased to be a distinct enterprise.]
(3)The condition mentioned in this subsection is that, in relation to the supply of goods of any description, at least one-quarter of all the goods of that description which are supplied in the United Kingdom, or in a substantial part of the United Kingdom—
(a)are supplied by one and the same person or are supplied to one and the same person; or
(b)are supplied by the persons by whom the enterprises concerned are carried on, or are supplied to those persons.
(4)The condition mentioned in this subsection is that, in relation to the supply of services of any description, the supply of services of that description in the United Kingdom, or in a substantial part of the United Kingdom, is to the extent of at least one-quarter—
(a)supply by one and the same person, or supply for one and the same person; or
(b)supply by the persons by whom the enterprises concerned are carried on, or supply for those persons.
[(4A)The condition mentioned in this subsection is that, in relation to the supply of goods of any description—
(a)at least one-quarter of all goods of that description which were supplied in the United Kingdom, or in a substantial part of the United Kingdom, were supplied by or to the person or persons by whom the enterprise was carried on, and
(b)that supply was made in connection with activities of the enterprise by virtue of which it was a relevant enterprise.
(4B)The condition mentioned in this subsection is that, in relation to the supply of services of any description—
(a)the supply of services of that description in the United Kingdom, or in a substantial part of the United Kingdom, was to the extent of at least one-quarter of all the services of that description, supply by or for the person or persons by whom the enterprise is carried on, and
(b)that supply was made in connection with activities of the enterprise by virtue of which it was a relevant enterprise.]
[...]
23A. Relevant enterprises
(1)In section 23 “relevant enterprise” means an enterprise the activities of which consist in or include—
(a)developing or producing restricted goods;
(b)holding information (including but not limited to information comprised in software and documents such as blueprints, manuals, diagrams and designs) that—
(i)is capable of use in connection with the development or production of restricted goods; and
(ii)is responsible for achieving or exceeding the performance levels, characteristics or functions of the restricted goods that are specified in the relevant export control legislation;
(c)owning, creating or supplying intellectual property relating to the functional capability of—
(i)computer processing units;
(ii)the instruction set architecture for such units;
(iii)computer code that provides low level control for such units;
(d)designing, maintaining or providing support for the secure provisioning or management of—
(i)roots of trust of computer processing units;
(ii)computer code that provides low level control for such units;
(e)research into—
(i)quantum computing or simulation;
(ii)quantum imaging, sensing, timing or navigation;
(iii)quantum communications; or
(iv)quantum resistant cryptography;
(f)developing or producing anything designed for use in—
(i)quantum computing or simulation;
(ii)quantum imaging, sensing, timing or navigation;
(iii)quantum communications; or
(iv)quantum resistant cryptography;
(g)supplying services employing—
(i)quantum computing or simulation;
(ii)quantum imaging, sensing, timing or navigation;
(iii)quantum communications; or
(iv)quantum resistant cryptography.
(2)In this section—
“intellectual property” means—
(a) any patent, trade mark, registered design, copyright or design right,
(b) any right under the law of a country or territory outside the United Kingdom corresponding to, or similar to, a right within paragraph (a), or
(c) any information or technique not protected by a right within paragraph (a) or (b) but having industrial, commercial or other economic value;
“quantum communications”—
(a) means the transmission of information, utilising the properties of quantum mechanics, in particular superposition or entanglement, and
(b) includes the establishment of cryptographic keys and the generation of true random numbers using a quantum physical process;
“quantum computing or simulation” means the study, simulation or realisation of systems that utilise certain properties of quantum mechanics, in particular superposition or entanglement, to process information, run algorithms or perform operations on data;
“quantum imaging” means utilising certain properties of quantum mechanics, in particular superposition or entanglement, to create images of objects with a resolution or other imaging criteria that is beyond what is possible in non-quantum optics;
“quantum navigation” means utilising certain properties of quantum mechanics, including measurements of suspensions of atoms or ions, to establish the location or movement of objects with a resolution or sensitivity that is beyond what is possible in non-quantum devices or systems;
“quantum resistant cryptography” means methods of securing information or data being transmitted or stored, including by non-quantum means, with a view to resisting attack by a quantum computer;
“quantum sensing” means utilising certain properties of quantum mechanics, including measurements of suspensions of atoms or ions, to determine a property or rate of change in the property of an object, or the effect of an object on a measurable quantity, with a resolution or sensitivity that is beyond what is possible in non-quantum devices or systems;
“quantum timing” means utilising certain properties of quantum mechanics, including measurements of suspensions of atoms or ions, to provide a timing signal with a resolution or sensitivity that is beyond what is possible in non-quantum devices or systems;
“relevant export control legislation” means—
(a) Schedules 2 and 3 to the Export Control Order 2008;
(b) the Schedule to the Export of Radioactive Sources (Control) Order 2006;
(c) Annex I to Council Regulation (EC) No. 428/2009;
“restricted goods” means goods, software or information the export or transfer of which is controlled by virtue of their being specified in the relevant export control legislation but excluding any goods, software or information which are controlled only to the extent that they are prohibited from being exported or transferred to one country only;
“roots of trust”—
(a) means hardware, firmware, or software components that are inherently trusted to perform critical security functions, and
(b) includes cryptographic key material bound to a device that can identify the device or verify a digital signature to authenticate a remote entity.
[...]
42 Intervention by Secretary of State in certain public interest cases
(1)Subsection (2) applies where—
(a)the Secretary of State has reasonable grounds for suspecting that it is or may be the case that a relevant merger situation has been created or that arrangements are in progress or in contemplation which, if carried into effect, will result in the creation of a relevant merger situation;
(b)no reference under section 22 or 33 has been made in relation to the relevant merger situation concerned;
(c)no decision has been made not to make such a reference (other than a decision made by virtue of subsection (2)(b) of section 33 or a decision to accept undertakings under section 73 instead of making such a reference); and
(d)no reference is prevented from being made under section 22 or 33 by virtue of—
(i)[section 22(3)(za), (a) or (e)] or (as the case may be) [33(3)(za), (a) or (e)]; or
(ii)[EU] law or anything done under or in accordance with it.
(2)The Secretary of State may give a notice to the [CMA] (in this Part “an intervention notice”) if he believes that it is or may be the case that one or more than one public interest consideration is relevant to a consideration of the relevant merger situation concerned.
(3)For the purposes of this Part a public interest consideration is a consideration which, at the time of the giving of the intervention notice concerned, is specified in section 58 or is not so specified but, in the opinion of the Secretary of State, ought to be so specified. [...]
(5)For the purposes of deciding whether a relevant merger situation has been created or whether arrangements are in progress or in contemplation which, if carried into effect, will result in the creation of a relevant merger situation, sections 23 [to 30] (read together with section 34) shall apply for the purposes of this Chapter as they do for the purposes of Chapter 1 but subject to subsection (6).
[...]
55 Enforcement action by Secretary of State
(1)Subsection (2) applies where the Secretary of State has decided under subsection (2) of section 54 within the period required by subsection (5) of that section to make an adverse public interest finding in relation to a relevant merger situation and has published his decision within the period so required.
(2)The Secretary of State may take such action under paragraph 9 or 11 of Schedule 7 as he considers to be reasonable and practicable to remedy, mitigate or prevent any of the effects adverse to the public interest which have resulted from, or may be expected to result from, the creation of the relevant merger situation concerned.
(3)In making a decision under subsection (2) the Secretary of State shall, in particular, have regard to the report of the [CMA] under section 50.
(4)In making a decision under subsection (2) in any case of a substantial lessening of competition, the Secretary of State may, in particular, have regard to the effect of any action on any relevant customer benefits in relation to the creation of the relevant merger situation concerned.
[...]
58 Specified considerations
(1)The interests of national security are specified in this section.
(2)In subsection (1) “national security” includes public security; and in this subsection “public security” has the same meaning as in article [21(4) of the EC Merger Regulation] .
[(2A)The need for—
(a)accurate presentation of news; and
(b)free expression of opinion;in newspapers is specified in this section.
(2B)The need for, to the extent that it is reasonable and practicable, a sufficient plurality of views in newspapers in each market for newspapers in the United Kingdom or a part of the United Kingdom is specified in this section.
(2C)The following are specified in this section—
(a)the need, in relation to every different audience in the United Kingdom or in a particular area or locality of the United Kingdom, for there to be a sufficient plurality of persons with control of the media enterprises serving that audience;
(b)the need for the availability throughout the United Kingdom of a wide range of broadcasting which (taken as a whole) is both of high quality and calculated to appeal to a wide variety of tastes and interests; and
(c)the need for persons carrying on media enterprises, and for those with control of such enterprises, to have a genuine commitment to the attainment in relation to broadcasting of the standards objectives set out in section 319 of the Communications Act 2003.]
[(2D)The interest of maintaining the stability of the UK financial system is specified in this section (other than for the purposes of sections 67 and 68 or references made, or deemed to be made, by the European Commission to the OFT under article 4(4) or 9 of the EC Merger Regulation).]
(3)The Secretary of State may by order modify this section for the purpose of specifying in this section a new consideration or removing or amending any consideration which is for the time being specified in this section.
(4)An order under this section may, in particular—
(a)provide for a consideration to be specified in this section for a particular purpose or purposes or for all purposes;
(b)apply in relation to cases under consideration by the [CMA, OFCOM] or the Secretary of State before the making of the order as well as cases under consideration on or after the making of the order.
[...]
66 Decision and enforcement action by Secretary of State
(1)Subsection (2) applies where the Secretary of State has received a report of the [CMA] under section 65 in relation to a special merger situation.
(2)The Secretary of State shall, in connection with a reference under section 62(2) or (3), decide the questions which the [CMA] is required to decide by virtue of section 63(1) to (3).
(3)The Secretary of State shall make and publish his decision under subsection (2) within the period of 30 days beginning with the receipt of the report of the [CMA] under section 65; and subsection (8) of section 54 shall apply for the purposes of this subsection as it applies for the purposes of subsection (5) of that section.
(4)In making his decisions under subsection (2), the Secretary of State shall accept the decisions of the report of the [CMA] under section 65 as to whether a special merger situation has been created or whether arrangements are in progress or in contemplation which, if carried into effect, will result in the creation of a special merger situation.
(5)Subsection (6) applies where the Secretary of State has decided under subsection (2) that—
(a)a special merger situation has been created or arrangements are in progress or in contemplation which, if carried into effect, will result in the creation of a special merger situation;
(b)at least one consideration which is mentioned in the special intervention notice concerned is relevant to a consideration of the special merger situation concerned; and
(c)taking account only of the relevant consideration or considerations concerned, the creation of that situation operates or may be expected to operate against the public interest;and has so decided, and published his decision, within the period required by subsection (3).
(6)The Secretary of State may take such action under paragraph 9 or 11 of Schedule 7 as he considers to be reasonable and practicable to remedy, mitigate or prevent any of the effects adverse to the public interest which have resulted from, or may be expected to result from, the creation of the special merger situation concerned.
(7)In making a decision under subsection (6), the Secretary of State shall, in particular, have regard to the report of the [CMA] under section 65." (Enterprise Act 2002 (UKPGA 2002 c. 40); last amended on 11.06.2018; Sections 23, 23A, 42, 55, 58, and 66; see also SCHEDULE 7: Enforcement regime for public interest and special public interest cases, and SCHEDULE 8: Provision that may be contained in certain enforcement orders)
Enterprise Act 2002 (UKPGA 2002 c. 40); last amended on 11.06.2018; Sections 23, 23A, 42, 55, 58, and 66; see also SCHEDULE 7: Enforcement regime for public interest and special public interest cases, and SCHEDULE 8: Provision that may be contained in certain enforcement orders
[<a href="https://www.legislation.gov.uk/ukpga/2002/40/contents/2018-06-11">Act</a>],[<a href="https://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=DAF/INV/RD(2018)7&docLanguage=En">Other</a>]