British women crash out of relay after blundering day in the pool

The disappointment came after Caitlin McClatchy had been withdrawn from the heats of the 100m freestyle to allow her to rest for an expected appearance in the final.

That gamble taken by performance director Michael Scott and women's coach Ben Titley backfired spectacularly.

Sinking fast: Joanne Jackson can't help Britain through the women's 4x200m freestyle relay heat

After the success of Joanne Jackson and Rebecca Adlington in the 400m freestyle earlier in the week, the British relay team were expected to challenge for a medal in Thursday morning's final.

But a sixth-place finish in their heat in a time of 7min 56.16sec saw the British squad of Jackson, Mel Marshall, Hannah Miley and Fran Halsall come ninth overall, more than half a second behind eighth-placed Japan.

'We were a medal prospect but we are very, very, very disappointed," said Marshall. 'It's been a great few days but that's a big slap in the face. But we have to try and turn it around now.

'We are absolutely gutted. We're disappointed for everyone at home who supported us but that's sport, that's why everyone watches it.

'A lot of teams swam better than we expected. I think 7:56 is a great time but unfortunately it wasn't great enough to get in there. It's not a nice position to be in after thinking we were going to go in for a medal tomorrow.

'I think we will go and have a bit of a tear, let it all out, have a swim down and we have some people who need our support tomorrow.'

The failure was particularly hard on Halsall, who had earlier set a new British record in the 100m freestyle to qualify for the semi-finals in a time of 53.93.

Stars earning their stripes: America's Caroline Burckle, Kim Vandenberg and Christine Marshall cheer on team-mate Julia Smit

But her split of 2:00.07 on the final leg saw the British team surpassed by Italy, Australia, Hungary and Japan in the dash for places in the final.

There was additional disappointment earlier in the session when Kirsty Balfour recorded a time well short of her personal best in the 200m breaststroke as she missed out on a place in the semi-finals.

Balfour posted a disappointing time of 2:27.87  to fall well short of the last 16 while American Rebecca Soni set an Olympic record of 2:22.17 to qualify for the semi-finals, more than 1.5 seconds ahead of 100m champion Leisel Jones of Australia.

Britain's men had more to cheer about as three swimmers made it through to the semi-finals.

Liam Tancock and James Goddard both advanced in the 200m individual medley as Michael Phelps cruised into the semi-finals along with fastest qualifier - and fellow American - Ryan Lochte as well as Hungarian Laszlo Cseh.

Goddard qualified in 13th position with Tancock in 14th with just 0.05 secs separating the two British swimmers.

'Making the semi-final is the main thing,' said Goddard. 'So hopefully I can refocus for tomorrow and put in a best time.

'I definitely have a lot more in me. I have to have a look at my stroke and then try and get into the final.

'My goals were to take it one round at a time and my first goal was to make the semi-final. Next it's to make the final and re-evaluate my goals.'

Gregor Tait made it through to the semi-finals of the 200m backstroke with a time of 1:57.03, qualifying in fifth position behind fastest qualifier Lochte and second-placed Aaron Peirsol, the joint world record holders in the event.