Asterion Industrial Partners, an independent European infrastructure investment manager, has joined the consortium led by Macquarie Asset Management (MAM) 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.
Southern Water is a fully regulated utility serving c.4.7 million customers in the South-East of England. The company provides public wastewater collection and treatment across Hampshire, the Isle of Wight, West Sussex, East Sussex and Kent, and public water supply and distribution across approximately half of this area.
The investment marks Asterion’s entry into the UK water sector and reflects its strategy of investing in essential infrastructure assets, supported by long-term capital and operational expertise.
The new capital follows £900 million of equity committed during 2025 and will deliver the full £1.2 billion equity support package announced by the Company in July 2025. Combined with the over £1.65 billion invested since MAM’s initial acquisition in 2021, total equity investment in Southern Water now stands at more than £2.8 billion. The equity commitment will continue to support a meaningful operational turnaround that accelerated through the first year of the 2025–2030 regulatory period, underpinned by a significant step-up in investment, with more than £1.1 billion deployed over the year as Southern Water began delivering its AMP8 programme.
Southern Water’s AMP8 record investment programme is aimed at enhancing infrastructure capacity and resilience to meet regulatory and environmental requirements, climate-related challenges and customer expectations.
Jesús Olmos, CEO and Founding Partner of Asterion Industrial Partners, said: “We are pleased to support Southern Water through this investment, which provides primary capital to help fund a significant capex programme focused on strengthening and modernising essential water infrastructure. We are equally pleased to partner with Macquarie Asset Management and to support the next phase of Southern Water’s development alongside them.
This transaction marks Asterion’s entry into a new sector in one of our core geographies, and is fully aligned with our strategy of backing essential infrastructure with long-term capital and industrial expertise. We see a strong opportunity to support Southern Water’s operational improvement, while contributing to the long-term resilience of critical infrastructure in the UK.”
Martin Bradley, Senior Managing Director at Macquarie Asset Management, said: “A year ago we set out a clear commitment to Southern Water and today’s announcement of an additional £300 million of equity support delivers the full £1.2 billion investment package announced in 2025. We are pleased to welcome Asterion Industrial Partners as a new minority shareholder, reflecting growing confidence in Southern Water’s management team, its progress and its future plans.
While there is more to do, the focus remains on continued delivery. This capital supports the sector’s largest growth programme relative to its size, with the company doubling the investment per household in the region for the benefit of its customers and the environment.”
About Asterion Industrial Partners:
Asterion Industrial Partners is an independent investment management firm focused on European infrastructure in the mid-market. Founded in 2018 and with $10bn under management, the firm invests in essential infrastructure across the energy, digital, utilities and mobility sectors, with a hands-on, industrial approach that prioritizes long-term value creation and sustainability. Asterion Industrial Infra Fund III, which closed in September 2025, reached total commitments of €3.4 billion. For more information, please visit www.asterionindustrial.com
About Macquarie Asset Management:
Macquarie Asset Management (MAM) is a leading global asset manager, trusted by institutions, individuals and communities to responsibly manage £376 billion in assets. MAM provides clients with a diverse range of investment solutions that seek to deliver superior risk-adjusted returns. Macquarie Asset Management is part of Macquarie Group, a diversified global financial services group operating in asset management, retail and business banking, wealth management, as well as advisory, and risk and capital solutions across debt, equity, financial markets and commodities. Founded in 1969, Macquarie Group employs over 19,100 people in 30 markets and is listed on the Australian Securities Exchange
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