The men's relay team have defended their over zealous celebrations as they came first in the 4x400m relay heat.
The women's relay took place first and Olympic champion Christine Ohuruogu almost cost Britain a place in the final of the 4x400 metres relay in Beijing.
Ohuruogu ran the final leg in the Bird's Nest stadium and took over in second place behind Russia after good runs by Nicola Sanders, heptathlete Kelly Sotherton and 800m specialist Marilyn Okoro.
With the top three in each semi-final qualifying automatically, Ohuruogu looked to have an easy task but almost took it too easy on the home straight as the Russian quartet strode to victory.
Ohuruogu then let Cuba's Indira Terrero go past and was almost caught by Germany's Claudia Hoffmann before looking up at the big screen and putting in a vital late burst to finish third in three minutes 25.48 seconds.
"I was just told to qualify so I was taking it easy but I didn't see the German," Ohuruogu admitted.
Sotherton, in the side after Lee McConnell was forced to pull out with a quad muscle tear, added: "I felt that was a very sensible race for me. I set a pretty good pace.
"I was petrified getting the baton from Nicola and passing it on to Marilyn but I think we'll step it up tomorrow. I'm only in the team because Lee is not able to compete and I hope I've done her justice."
In the men's event, the quartet of Andrew Steele, Robert Tobin, Michael Bingham and individual finalist Martyn Rooney cruised into the final by winning the second semi-final in the fastest time of 2:59.33.
However, Rooney's taunting of the Bahamas and Jamaica before he crossed the line was completely unwarranted and the United States remain hot favourites after winning their semi despite resting individual gold and silver medallists LaShawn Merritt and Jeremy Wariner.
Rooney defended his premature celebrations, saying: "The relay is all about having fun. We are at the Olympics, we are running well, it was a quick time without doing any real work so I enjoyed it.
"The rest of the team are all pretty fresh and left with me very little to do which was what I wanted. It was good fun, tomorrow we are going to bring on our A game and take on the best."
Rooney acknowledged the American quartet are huge favourites but hinted the Jamaican team could spring a surprise by adding Usain Bolt to their line up.
"The Americans have the best team obviously with the first three in the 400m and then it's between us and the Jamaicans, although they might bring in a special guy," he added. "The Russians broke their national record but we are pretty confident."
Jade Johnson produced a highly-consistent series in the long jump final but had to settle for seventh place with a best of 6.64m in the second round.
Brazil's Maurren Maggi led after the opening round with a jump of 7.04m and dramatically held onto the gold medal as defending champion Tatyana Lebedeva jumped 7.03m in the final round.
Blessing Okagbare, who only made the final after Ukraine's Lyudmila Blonska was thrown out of the Games for failing a drugs test, took bronze with a best of 6.91m.
There was yet more baton-changing drama in the final of the women's 4x100m relay with both Britain and hot favourites Jamaica failing to finish.
Both teams made a mess of the second changeover, Montell Douglas failing to get the baton to Emily Freeman - who may have gone off too early - and Sherone Simpson and Kerron Stewart doing the same for the Jamaicans.
That left the Russian quartet clear to take gold ahead of Belgium and Nigeria.