Winchester Cathedral was once in danger of collapsing - and part of the solution involved sending a man underneath it in a diving suit.
His name was William Walker.
In the early 1900s the ancient cathedral was sinking into waterlogged, marshy ground. Huge cracks appeared and its foundations needed urgent support.
Walker was an experienced deep-water diver. Between 1906 and 1911 he descended into flooded trenches beneath the cathedral and worked for around six hours a day in near-total darkness.
His diving suit was a world away from modern equipment: a heavy suit, lead boots and a great copper helmet, with air pumped to him through a hose. The muddy water was so opaque that he often had to work by touch.
Walker helped stabilise the foundations by placing bags of concrete beneath them. The wider underpinning project used more than 25,000 bags of concrete, around 115,000 concrete blocks and 900,000 bricks.
Only after the underwater support was in place could the water be safely pumped away and permanent foundations built.
Today visitors walk through Winchester Cathedral looking up at soaring stone arches and beautiful windows.
But one of the most extraordinary parts of its story happened underneath their feet - where a diver spent years working blind in cold, muddy water to help keep the whole building standing.
Discover more astonishing Winchester history with our Winchester Quiz Trail & City Souvenir:
