Athletics:Great Britain's sprint relay woes continued as another baton changeover mistake cost them a place in the 4x100 metres final at the Olympic Stadium. The host nation were disqualified when anchor leg runner Adam Gemili set off too early as he was about to take the baton from Danny Talbot.
The 18-year-old slowed down dramatically, but the changeover still occurred outside the designated area.
Gemili sprinted for the line and came home second, but the fact he immediately put his hands to his head told the story.
The mistake continues a woeful record for Britain in the event, who, aside from the one glorious exception at the Athens 2004 Olympics, have lurched from one failure to the next.
Dropped batons at the Olympics in Atlanta (1996) and Sydney (2000) and the World Championships in Edmonton (2001), along with a disqualification at the last Olympics in Beijing and the World Championships in Daegu (2011) have ended their chances.
They also went out in the first round at the last European Championships in Barcelona two years ago, while at the most recent Europeans earlier this summer they also failed to get the baton round.
Jamaica, without Usain Bolt, qualified safely, but the United States were the quickest through in a new national record of 37.38 seconds.
Gemili told the BBC: "I went off and maybe I went a bit harder...I don't know. We really could have been in contention in the final had we made it.
"It really is disappointing. I think I went on the check mark maybe a tiny bit early."
For Chambers, who ran the second leg, this was almost certainly his last race at an Olympics. And he was keen to keep his teenage team-mate's spirits up.
He said: "We're proud to have been here representing our country. Adam's had a fantastic start to his season. This is his first or second season in athletics and he was asked to do a big task.
"I'm proud of him more than anything else. We have to build as a team and hopefully can do better throughout the summer and next year."
There was better news for Great Britain's women's 4x400m team as they booked their place in Saturday's final by finishing a comfortable third in their heat.
The quartet of Shana Cox, Lee McConnell, Eilidh Child, Christine Ohuruogu, the individual silver medallist, clocked three minutes 25.05 seconds.
Britain, who are the reigning world indoor champions, finished behind heat winners the United States and Russia.
The women's 4x400m team booked their place in tomorrow's final by finishing a comfortable third in their heat.
The quartet of Shana Cox, Lee McConnell, Eilidh Child and Christine Ohuruogu, the individual silver medallist, clocked 3mins 25.05 secs.
Britain, who are the reigning world indoor champions, finished behind heat winners the United States and Russia.
The top two were well clear and look set to battle it out for the gold, but the hosts will fancy their medal chances, with Ohuruogu especially looking like had more in the tank and Perri Shakes-Drayton to come in.
Ohuruogu said: "We are a good team so we knew we were going to get through. I've recovered from the individual, I had four days so it's loads of time."
Child added: "It was just a case of getting it round safely and securing that spot for tomorrow. So job done really."
Cox, who ran the first leg, said: "I was happy with it, just trying to put myself in a good position for Lee and the rest of the team."
McConnell added: "There was a little bit of barging going into the bend but it was good fun, I held my position so I can't complain."
Sophie Hitchon finished 12th in the hammer final after failing to repeat her impressive qualifying throw.
The 21-year-old, who broke her British record with a 71.98m throw in qualifying, could only manage a best of 69.33m today.
It would have taken a huge personal best to make the top-eight cut in any case, though.