Staff working on the super sewer project won the opportunity to cycle 10km through the giant tunnel last month after raising more than £1,500 in a charity raffle. 

Tickets were raffled off to raise money for Tideway’s staff charity partners, Felix Project and Time & Talents, with six lucky winners given the once-in-a-lifetime opportunity to participate in what is thought to be London’s deepest ever bike ride. 

Starting at Tideway’s site in Battersea, the cyclists cycled east toward Blackfriars and back again, completing a total of 10km beneath central London. 

As the tunnel is built on a slight slope, to allow storm flows to travel via gravity toward the treatment works, the cyclists rode the first leg of the ride ‘downhill’ and the return leg ‘uphill’, although the 1:790 gradient meant the climb was almost imperceptible. 

Heather Glass, Tideway regulation manager, told Cycling Weekly: “ I've been on the project for seven years. But it was my first time down in the tunnel.

“It’s definitely the weirdest ride I've done. It's really quite something, we were lowered down on a man rider, which is a cage that hangs from a crane, to the bottom of the shaft, where the bikes were waiting for us. Then we set off. I feel really privileged to have been able to be one of the few people to do it.”