This raise is a clear vote of confidence in the private equity-infrastructure crossover, as investors keep backing strategies built around resilient, asset-backed cashflows and essential services.
MML Capital Partners has reached a final close of MML Keystone I at EUR 935 million for its debut Keystone strategy, according to a recent announcement. The fund closed in December 2025 and was oversubscribed, with Preqin data cited as placing it among the largest fundraises on record for a new European strategy.
What MML Keystone is selling, and why LPs are buying
Keystone’s pitch is straightforward: invest in high-growth, asset-backed businesses providing essential services in the UK and Europe. The strategy positions itself at the intersection of private equity and infrastructure, a segment that has benefited from sustained institutional demand for more defensive growth and inflation-resilient characteristics.
MML says commitments came from a globally diverse group of blue-chip institutional investors across Europe, North America, Asia, Australia, and the Middle East. That mix matters. It signals that the “core-plus” style appetite is no longer regionally constrained and that newer European strategies can still scale quickly when they offer a clean, differentiated risk profile.
The strategy: megatrends, but tied to assets
Keystone is framing its opportunity set around megatrends, including:
- Circular economy
- Energy transition
- Digitalisation
- Access to healthcare and education
The differentiator is that these themes are not being pursued as pure growth narratives. The strategy emphasises asset backing and essential-service characteristics, which tends to pull underwriting away from “blue-sky” assumptions and toward contractual revenues, utilisation, and replacement cycles.
MML points to prior Keystone-related successes, including investments such as ekeg (reusable containers) and Lowe (sustainable refrigeration-as-a-service). Both examples sit neatly in today’s institutional sweet spot: operational assets tied to sustainability outcomes, with a service layer that can compound returns.
Platform credibility: fundraising momentum at MML
The close also builds on a wider fundraising run at the firm. MML Capital Partners said it successfully closed five funds raising over EUR 2.4 billion in 2025, demonstrating that Keystone is not a one-off outlier but part of a broader capital formation capability.
Leadership messaging has focused on execution: Co-Managing Partner Andrew Honan highlighted the team’s capability in driving sustainable growth for portfolio companies. In practical terms, that puts the burden on sourcing and operational delivery in a segment where competition is rising and pricing discipline can be tested.
What to watch next
For LPs, the key question is whether the strategy can consistently find businesses that are both high-growth and asset-backed without drifting into crowded infrastructure-lite deals or, conversely, traditional buyouts with only a thematic overlay.
Execution risks are familiar but real: integration complexity in essential-services platforms, regulatory exposure in certain service lines, and the challenge of scaling operating capabilities fast enough to match fund size. The upside is that the mandate is aligned with where institutional portfolios are moving: durable services, tangible assets, and sustainability-linked capex cycles.
With Keystone’s debut fund now closed at scale, the market will judge it less on narrative and more on deployment pace, deal selectivity, and whether the PE-infrastructure blend produces the resilience it is designed to deliver.