In the hills above Los Gatos, California, a small team of British engineers has done what the state’s emergency services could not. As wildfires tore through the Santa Cruz Mountains last month, consuming homes and livelihoods, a single steel bunker – engineered by retired former RAF engineer John Trelawney and his daughter Emma – became the difference between survival and ruin for 47 families.
The Trelawneys, from Sheffield, had moved to California five years ago. John, 64, had spent decades designing blast-proof shelters for military installations. Emma, 34, an architect specialising in sustainable housing, saw the gap between military-grade protection and civilian fireproofing. “We wanted to build something that could withstand a firestorm but also be a home,” Emma said. “Not a concrete tomb. A haven.”
The bunker, which they call the ‘Steel Haven’, is a prefabricated structure made of layered steel with a self-contained air filtration system, a water tank and solar panels. It sits partially buried, with a curved roof designed to deflect heat and embers. The interior is arranged like a small flat, with sleeping quarters, a kitchen, and a communications hub. It cost £180,000 to build – a fraction of the typical luxury wildfire shelter.
When the Creek Fire swept through Los Gatos in August, the Trelawneys’ prototype was the only structure in its neighbourhood left standing. “I saw the flames coming over the ridge,” said Maria Santos, a retired nurse who sheltered with her husband and three children. “The house next door exploded. Inside the bunker we could feel the heat through the walls, but the air was clean. John had rigged up a radio. We listened to the fire reports. It was terrifying, but we were safe.”
John and Emma had spent the previous weekend installing the bunker for the Santos family. “We had to rush. The fire warnings were already out,” Emma said. “But seeing them come out alive, seeing the house reduced to ash and the bunker unscathed – that was the proof we needed.”
The local fire chief, Mark Delaney, has since urged the town council to adopt the design for new developments. “I’ve seen too many bodies in burned-out cars,” he said. “This thing works. It’s not a luxury. It’s a lifeboat.”
The Trelawney’s company, Haven Systems, has been flooded with orders from across California and beyond. They are now building a factory in San Jose to meet demand, hiring local workers. But John is wary of turning the bunker into a commodity for the rich. “We are working on a community model: a shared shelter for a street of houses. That brings the cost down to what a family can afford,” he said. “Resilience shouldn’t be a postcode lottery.”
For Emma, the project is also personal. Her mother died in the Grenfell Tower fire in London in 2017. “I saw what happens when buildings fail,” she said. “I wanted to build something that would not fail. Something that gives people a second chance.”
The Steel Haven may not be pretty. It sits in the garden like a giant metal mushroom. But for the families of Los Gatos, it is a monument to survival. British engineering, rooted in a northern industrial tradition of making things that last, has found a new frontier. And it is saving lives.
