Asterion's 20% stake in Southern Water, 2026

analysisAsterion announced the investment in a press release of 22 June 2026, before EU merger clearance and completion. According to the release, Asterion joined the consortium led by Macquarie Asset Management as a new minority shareholder with approximately 20 per cent in Southern Water, committing the majority of the £300 million of equity investment, subject to customary regulatory approvals; the new capital completed the £1.2 billion equity support package announced by the company in July 2025 and marked Asterion's entry into the UK water sector. A press report the same day, citing Macquarie, said that Asterion would acquire a 20% stake in Southern Water, subject to regulatory approval. Ofwat and the group's financial statements, by contrast, describe the stake as a minority shareholding in the group, that is in a holding company of Southern Water, not as a direct shareholding in Southern Water Services Limited. The release quotes Martin Bradley, described there as Senior Managing Director at Macquarie Asset Management, the manager of the majority investor, as saying that the additional £300 million of equity support delivered the full £1.2 billion investment package announced in 2025 and welcoming Asterion Industrial Partners as a new minority shareholder in Southern Water. It also quotes Jesús Olmos, described there as CEO and Founding Partner of Asterion Industrial Partners, as saying that the investment provides primary capital for Southern Water's capital programme and marks Asterion's entry into a new sector in one of its core geographies; the press report called him "AIP Chief Executive" when quoting the same statement. These are the titles used in June 2026; Spain's CNMV register lists him as chairman (presidente), director and consejero delegado (managing director) of Asterion Industrial Partners SGEIC, S.A. What followed is set out below: the European Commission decided on 20 July 2026 not to oppose the transaction, and Ofwat states that it completed in August 2026 with Asterion taking a 20% minority shareholding, the £300 million being expected to be drawn by 31 March 2027. ^{1 2 3 4}

analysisSW (Finance) I PLC's financial statements for the year ended 31 March 2026 record the same announcement: on 22 June 2026 the Southern Water group announced a further £300 million of committed equity from Sandstone Bidco Limited, to be drawn down on or around 31 March 2027. Subject to EU Merger Regulation clearance, the majority was to be funded by subscriptions for new shares in the Southern Water group by Asterion Industrial Partners, described as an independent European infrastructure investment manager headquartered in Madrid, and the balance by funds managed by Macquarie Asset Management (MAM); following completion Asterion was to become a new indirect minority shareholder of the group, with MAM-managed funds remaining the majority shareholder. Ofwat's consultation of September 2026 gives the same account and records what followed: the commitment was unconditional except for EU merger clearance in respect of Asterion's investment, the European Commission cleared the acquisition in July 2026 — its decision not to oppose the concentration is dated 20 July 2026 — and the transaction completed in August 2026 with Asterion taking a 20% minority shareholding in the group. Ofwat describes the commitment as binding and expected to be drawn down in full on or around 31 March 2027. ^{5 4}

analysisOn 22 June 2026 the European Commission received notification of a proposed concentration, case M.12488 – ASTERION / MACQUARIE / SOUTHERN WATER, published in the Official Journal (C/2026/3488) on 1 July 2026 as a candidate case for the simplified procedure. The notice names as undertakings concerned Asterion Industrial Partners, SGEIC, S.A. (Spain); MSCIF Sandstone Ventures S.à r.l. (Luxembourg), controlled by Macquarie Group Limited (Australia); and Southern Water Services Limited, controlled by Macquarie Group Limited. According to the notice, Asterion and Macquarie Group Limited would acquire joint control of Southern Water by way of purchase of shares. The notice gives only this notified description of the transaction: it states neither the size of Asterion's stake nor the rights on which joint control rests, and Ofwat and the company describe Asterion's interest as a 20% minority shareholding in the group. On 20 July 2026 the Commission decided not to oppose the concentration and declared it compatible with the internal market under Article 6(1)(b) of the EC Merger Regulation; the decision was published in the Official Journal (C/2026/4127) on 28 July 2026. ^{1 2 3}

analysisOfwat, notified of a change in ownership affecting Southern Water Services Limited, opened a consultation on 23 September 2026 on whether any issues arise from the change of control, asking for views on its assessment of the new owner and on its identification of the Ultimate Controllers. It states that a new investor has taken a substantial minority stake in a holding company of Southern Water and in its view meets the licence definition of an Ultimate Controller. The consultation closes on 30 October 2026; it was still open when the evidence was collected in October 2026, and no outcome is in the record. Ofwat identifies the new investor as funds managed by Asterion Industrial Partners SGEIC, S.A., registered in Madrid and regulated by Spain's financial regulator, the CNMV, under register number 138, and describes Asterion as an independent European infrastructure investment manager established in 2018 and headquartered in Madrid. Southern Water, Ofwat states, is the fund's first direct investment in an appointed water and sewerage undertaker in England and Wales, and apart from Southern Water Asterion has no investment or other interest in any other UK water business; Asterion's senior leadership brings direct UK water-sector expertise, several team members having previously held key roles at South Staffordshire Plc, including the positions of CEO and Chairman. Ofwat does not name these team members. It concluded that Asterion is a credible and experienced minority shareholder. Its assessment rests on information provided by the new owner and Southern Water and on its own review of public information, and Asterion confirmed to Ofwat that it is not aware of any actual or perceived conflicts of interest. ^{1 2}

analysisOfwat separates the holder of the stake from the company that controls it. According to Ofwat, Asterion Industrial Infra Fund III, FCR is the legal holder of the minority (20%) investment in Southern Water. The fund is a pool of assets without legal personality, with a diverse investor base and no single majority investor; under Spanish law its management, representation and powers of control are vested in Asterion Industrial Partners SGEIC, S.A., which Ofwat describes as exercising effective control over the fund without owning it. Ofwat describes Sandstone Water Holdings Limited as the last UK holding company of the Southern Water group and the company through which funds are invested in Southern Water. Certain matters are reserved to its board and shareholders, and under a shareholders' agreement certain investors, including Asterion, have a right to nominate one or more non-executive directors for appointment to the board of Southern Water. Ofwat names no party to that agreement other than Asterion, and it does not name the holding company in which Asterion's fund holds its 20%. Who owns and manages Asterion itself is set out on a separate page. ²

analysisBecause of its effective control over the fund and its right to nominate representation on Southern Water's board, which make it a person able to exert material influence over Southern Water, the consultation identifies Asterion Industrial Partners SGEIC, S.A. as an Ultimate Controller of Southern Water Services Limited. Asterion provided the required Ultimate Controller undertakings to Southern Water, dated 12 August 2026, which Ofwat considers compliant with the licence. Ofwat states that Macquarie Super Core Infrastructure Fund SCSp, Macquarie Asset Management Europe Sarl and Sandstone Water Holdings Limited, already identified as Ultimate Controllers of Southern Water, have each provided compliant undertakings, that their role is unaffected by the change in ownership and that their undertakings remain in place; it does not give the dates on which the three were first identified. It restates that Asterion Industrial Infra Fund III, FCR is the legal holder of a large minority investment (a 20% shareholding), with all management, representation and control powers in respect of the fund vested in Asterion. Ofwat identified no other new Ultimate Controllers and no issues under its board leadership, transparency and governance principles. These findings are stated in a consultation that invites views on the identification of the Ultimate Controllers; it closes on 30 October 2026, after the evidence cutoff, and no final decision is in the record. ^{1 2}

analysisSandstone Water Holdings Limited (company number 16482350) filed a confirmation statement made up to 28 May 2026 showing 81,376 ordinary shares, all held by MSCIF Sandstone Ventures S.à r.l. Its Companies House filing history then records two statements of capital following allotments of shares on 12 August 2026: one filed on 12 August 2026 showing share capital of GBP 81,380, and one filed on 21 August 2026 showing GBP 101,725.00. A resolution adopting new articles of association and the new memorandum and articles were filed on 21 August 2026. The return of allotment filed on 21 August 2026 records 20,345 ordinary shares of £1 allotted on 12 August 2026, after which 101,725 shares were in issue; 20,345 is exactly one fifth (20%) of 101,725. As an analysis, this dossier reads these filings as consistent with Asterion's fund having taken its 20% by subscribing for new shares in Sandstone Water Holdings, the company Ofwat describes as the one through which funds are invested in Southern Water. The identification of this allotment with Asterion's stake is an inference from the matching size and date: the return of allotment does not name the allottee, the retained records contain no later shareholder list of Sandstone Water Holdings, and Ofwat does not name the holding company in which the stake is held. ^{1 2 3 4}

analysisCompanies House's officers register for Sandstone Water Holdings lists Alter Domus (UK) Limited as company secretary since 13 November 2025, and two earlier directors: Richard Greenleaf (29 May 2025 to 3 March 2026) and Susana Durante Teixeira Gomes Leith-Smith (29 May 2025 to 20 December 2025). On 22 December 2025 the company's registered office moved from Ropemaker Place, 28 Ropemaker Street, London to care of Alter Domus (UK) Limited, 30 St Mary Axe, London. William David George Price was a director of Sandstone Midco Limited (company number 16482495), Sandstone Bidco Limited and Sandstone Water Holdings Limited from 20 December 2025 until his resignation on 12 August 2026. On that day Companies House recorded the appointment of Martin Bradley, Neil Robert Vint Corrigall, Adrian Peter Page and Stephen Glynn Hurrell as directors of Sandstone Water Holdings, and the end of the directorships of Catherine Isabelle Harber (director since 29 May 2025), Pooja Hitesh Shah (director since 3 March 2026) and Price. The four directors appointed on 12 August 2026 are listed as active on the officers register retrieved in October 2026. ^{1 2 3}

analysisSouthern Water's own board was expected to gain an Asterion nominee. In the chair's statement dated 15 July 2026, Southern Water's annual report for the year ended 31 March 2026 states that, following the recent equity transaction, Asterion Industrial Partners are expected to nominate a non-executive director; it also states that Martin Bradley and Steve Hurrell will join the Southern Water board as investor-nominated non-executive directors once Ofwat's new fitness and propriety processes are completed, and describes Will Price as an investor-nominated non-executive director who receives no fees from the company. This was a statement of intention as at July 2026: the retained records do not show whether, or whom, Asterion has nominated to Southern Water's board. ⁴

analysisOne of the four directors appointed to Sandstone Water Holdings on 12 August 2026, Adrian Peter Page, has the same first name and surname as a member of Asterion's Industrial Advisory Board. Asterion's website, on the page of its Southern Water press release retrieved in October 2026, describes Adrian Page as an Industrial Advisory Board member at Asterion Industrial Partners who was Group CEO, having previously been CFO, of South Staffordshire Plc, a UK water company. The website gives the name "Adrian Page" only and does not say that he holds any role in the Southern Water group. A Companies House officer record for Adrian Peter Page lists him as a director of South Staffordshire Water Plc (company number 02662742) from 1 July 1998 and of South Staffordshire Limited (04295398) from 4 December 2003, both until 29 April 2020; as a director of Waterflo Limited and Brightwater Limited from July 2019 to 29 April 2020; and as a director of Energy Assets Group Holdings Limited (12390729) since 2 July 2021, listed as active on the record retrieved in October 2026. ^{5 6 2 1}

analysisAs an analysis, this dossier treats the Adrian Peter Page appointed a director of Sandstone Water Holdings Limited on 12 August 2026, the Adrian Peter Page of the officer record just described, a second Companies House officer record separate from the one on the Sandstone Water Holdings register, and the "Adrian Page" whom Asterion's website lists as an Industrial Advisory Board member as one person. The basis is that the two Companies House records give the same full name and the same partial date of birth (not reproduced here), and that the website's career description, Group CEO and earlier CFO of South Staffordshire Plc, matches the second record's directorships of South Staffordshire Water Plc and South Staffordshire Limited until April 2020; Ofwat separately states, without naming them, that several Asterion team members previously held key roles at South Staffordshire Plc. The limits: no source states that Adrian Peter Page was appointed to the board of Sandstone Water Holdings as Asterion's nominee or that he represents Asterion; the records show only that his appointment was registered on the same day as the other board changes and share allotments of 12 August 2026. ^{1 6 5 7}