Investing to support Southern Water’s investment programme

• A consortium led by Macquarie Asset Management (MAM), together with Asterion Industrial Partners as a new minority shareholder, has committed an additional £300 million of equity to Southern Water (the Company)
• This commitment will deliver the £1.2 billion growth equity package announced in July 2025, taking shareholders’ total equity investment in Southern Water to more than £2.8 billion since 2021

A consortium led by Macquarie Asset Management (MAM) has committed an additional £300 million of equity to Southern Water. This follows £900 million of equity committed during 2025 and will deliver the full £1.2 billion equity support package announced in July 2025. This will bring the total equity investment made by MAM-managed funds and co-investors into Southern Water to more than £2.8 billion since MAM’s acquisition in 2021.

The majority of the latest £300 million equity commitment will be provided by funds managed by Asterion Industrial Partners (AIP), an independent European infrastructure investment manager headquartered in Madrid with around $10 billion in assets under management.  AIP’s binding equity commitment is subject to customary regulatory approvals and will see AIP join Southern Water as a ~20 per cent shareholder.

The equity invested to date has supported an operational turnaround that has accelerated through the first year of the new regulatory period to March 2026, underpinned by a step-change increase in new investment, with £1.1 billion deployed over the year as the company began delivering its 2025–30 programme.

In the first year of the AMP8 period (the year ended 31 March 2026), Southern Water continued to make progress against its operational turnaround, delivering improvements across a number of measures including water supply interruptions, leakage and external sewer flooding, alongside a record level of capital investment in its network.

The company remains focused on addressing underlying drivers of pollution alongside improvements in operations, asset performance and targeted investment, building on progress since 2021.

Martin Bradley, Senior Managing Director, 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.”

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.”