text: Individual world champion James Guy swam a superb final leg after Dan Wallace, Robbie Renwick and Calum Jarvis had put Britain in contention.
  The US were led off by swimming great Ryan Lochte but could not hold on.
  "They've always been the best 4x200m team in the world but we really stepped our game up tonight," said Wallace.
  "It always makes you confident to have the world champion anchoring your relay but I think we set him up pretty well and it was a great race."
  Britain clocked a time of seven minutes 4.33 seconds to claim the nation's first ever men's relay gold at a World Championships, with the US and Australia completing the podium.
  The US had won the event, which will be part of the Olympic programme in Rio next year, at the last five World Championships.
  Guy, 19, won the individual title on Tuesday and took the British quartet from third to first on the final leg of the relay.
  "The way things have been going in racing and training, the work is paying off," said Guy. "The personal bests are finally dropping down."
  Britain now stand third in the overall medals table behind the United States and Australia with five gold, one silver and two bronze medals after six of eight days in Kazan.
  In Friday's other events, Andrew Willis finished fourth in the men's 200m breaststroke but Lizzie Simmonds failed to progress in the 200m backstroke.
  Ben Proud and Fran Halsall qualified for Saturday's 50m freestyle and butterfly finals respectively.
target: Great Britain's men overhauled the United States in a dramatic 4x200m freestyle relay final to win gold at the World Championships in Russia.