Ultra Challenge - Thames Bridges The popular and friendly Thames Bridges Trek that heads east from the Putney Bridge starts into the City - zig-zagging over 16 historic bridges, giving the best views of London's famous skyline and landmarks. 25km later, it's a finish line celebration in Southwark past the majestic Tower Bridge. Start: Putney Bridge Finish: Tower Bridge Registration fee: £5 Sponsorship target: £245 Mixed and self-funding options available Contact our supporter care team