Triathlon part of Olympic build-up
The Tri-City-Athlon on September 14 will see triathletes start the race in Paris in the morning for the swimming before getting on the Eurostar to Brussels.
This is where the cycling will take place, followed by another Eurostar trip to London for the running event. It is part of Eurostar's third level sponsorship of the London Games where the firm will be the official international rail services provider.
Lord Coe said: "We have got a Tri-City-Athlon which is at the coal face of helping young people understand what Olympic sport is about."