Great Britain have failed in their appeal against disqualification from the Olympic men's 4x400m relay semi-final in Rio.
Nigel Levine, Delano Williams, Matthew Hudson-Smith and Martyn Rooney finished first in two minutes 58.88 seconds.
Leg three runner Hudson-Smith was ruled to have had part of his foot out of the takeover zone when he began running.
British Athletics said it was "hugely disappointed" and confident the team would have won a medal in the final.
The appeal was rejected because video evidence was inconclusive, meaning the decision of the referee must be upheld.
Britain clocked the third fastest time behind Jamaica and the United States, who ran in the first semi-final.
Team GB's disqualification means Brazil progress to the final as the eighth-fastest qualifier.
Rooney, 29, told BBC Radio 5 live: "In the changeover you have to be between two red lines which are about 20 metres apart. You have to stay within those red lines.
"From then on there is a solid red line across the track which is about 10 metres before the finish line and 10 metres afterwards, and you have to exchange within the zones.
"I haven't seen it, but I can't see how any of us went outside those zones."
The women's quartet made it safely through to the final on Saturday.
"I haven't been involved in so much speculation as I have in the next 20 minutes," former Olympic champion Michael Johnson said after the men's race.
"It has to have been a judge that decided he saw something somewhere that they decided was an infringement, but I just can't think what that could be."