Piers Clark

Piers Clark has spent thirty years on a single, unglamorous problem, which is that the water sector is brilliant at inventing technology and terrible at actually buying it. He puts it more bluntly than I would: the industry is "technically incredibly competent" and knows exactly what to do, but when a promising trial produces good data, it tends to stay "a glossy thing" that nobody ever adopts into the core business. The bottleneck is adoption, not invention, and closing that gap has become the through-line of his whole career.

Piers Clark did not plan any of this. He took a BSc in environmental sciences and a PhD in civil engineering at the University of Southampton, went into water research, and by his mid-thirties was running a third of the engineering consultancy Mouchel as one of its managing directors. Then came two career bumps that, in his words, "felt absolutely disastrous" at the time. In December 2009 he shook hands on a management buyout of his division, and twenty-four hours later a hostile bid for the whole of Mouchel killed the deal in ten minutes. In 2010 he landed instead at Thames Water, heading an 800-person asset team and a billion-pound-a-year capital programme, and Isle, which had been the project name of that dead buyout, quietly became a company.

Isle Utilities started as what Piers Clark cheerfully calls a lifestyle business, just him consulting for Thames Water, until the small team behind an initiative he had founded at Mouchel, the Technology Approval Group (TAG, a sort of dragon's den where water utilities vet new technology together), was about to be made redundant. He took them on without thinking it through, rang his wife Stella to say he had "just gambled a quarter of a million pounds," and built Isle around them. Today TAG is roughly a third of an Isle that employs about 100 people across eight countries and works with more than 300 utilities, and it has screened over 10,000 technologies. He then spent a year inside Blackstone's billion-dollar water fund, decided he was not built to be a financier, and went back to the consultancy.

The Trial Reservoir is the idea that ties it all together, and the mechanism is the clever part. A water utility will happily run a pilot and then never buy the kit, which leaves the start-up that paid for the trial stranded, so Piers Clark inverted the order. The Trial Reservoir lends the money for the trial, but only on the condition that the utility has already agreed to adopt the technology if it hits the targets. When it works, the vendor repays the pot from the resulting contract and the money cycles into the next trial, which makes it an evergreen fund rather than a grant. Isle seeded it by redirecting the 25% of its profits it used to give to charity, and Piers got, in his telling, "a hell yes" from his shareholders. He walks through the whole model on the podcast.

The whole thing arrived, fittingly, by accident. On a 2021 family holiday in the Yorkshire Dales, on the day an IPCC climate report landed, Piers Clark had three beers and an out-of-character late coffee, lay awake, and the Trial Reservoir "pretty much came to me fully formed at 3 AM," excited enough that he woke Stella up. He launched it that November. He has since said he wants to spend his remaining years in water making the model endemic everywhere, in energy and transport too, with carbon mitigation as the metric he wants read out on his deathbed. For a man whose two biggest setbacks were a buyout and a private-equity job, it is a neat ending: the water sector's adoption problem, finally turned into a fund.

“I then rang my wife and said, Stella, I think I've just gambled quarter of a million pounds. Are we okay with that?”

That instinct, acting first and counting the cost afterwards, is most of why Isle exists at all, and why the Trial Reservoir got built while more cautious people were still writing the business case.