Team GB'S Great Britain men's 4x100 metres team have been disqualified after promising teen Adam Gemili took the baton outside of the designated box - despite finishing second.
In the heats, Gemili, running the final leg, was found to have set off too early as he waited for the baton from Danny Talbot, and the team were disqualified.
Gemili grabbed for the baton twice before heading over the line, watched by team mates Dwain Chambers and Christian Malcolm.
Britain's Adam Gemili reacts after a men's 4 X 100-meter relay heat
Jamaica won the race with Canada second and the Netherlands third, all three progressing.
Malcolm told the BBC: "It's unfortunate. It was a fantastic performance. This is a big stage, it can be overwhelming. These things happen."
Great Britain's Adam Gemili crosses the line in the mens 4x100
Gemili added: "It's disappointing, because we really could have been in contention. Maybe I went a tiny bit early. In a stadium like this it's hard to hear."
Talbot said: “I don’t know what happened, I just couldn’t catch him. I feel bad for the team. I’m really gutted that we’ve been disqualified, it’s devastating.”
The men's 4x100m has had a chequered past for Team GB, with the team dropping batons at the Olympics in Atlanta and Sydney, along with a disqualification in Beijing.