YORK swimming star Caroline Foot goes into her British championships semi-finals this evening knowing only a personal best effort would see her reach her third Olympic Games.

The national championships, being held in Sheffield, were doubling up as the Olympic trials for British swimmers wanting to secure a place at September's Sydney Games.

And butterfly specialist Foot - who finished fourth fastest in today's heats - entered the event knowing she had to not only win tomorrow's 100m final but also improve her best time by more than half a second to guarantee a place in the Great Britain squad.

Should she finish second, she will have to smash her personal best by a second to have any chance of completing a hat-trick of Olympic appearances, having captained the women's team in Atlanta '96 and swam at Seoul ' 88.

The Olympic committee have stipulated a 100m butterfly qualifying time of 61.14secs for the national champion, whereas if Britain were to enter the maximum two swimmers in the event, both will have to go under 60.7secs.

Foot's current lifetime best, set in Sheffield in May, stands at 61.7secs.

With national record holder Sue Rolph not involved in this event, Foot, 35, went into today's heats ranked third, behind Richmond teenager Nicola Jackson - the only competing Briton to have officially swam the Olympic qualifying time - and Margaretha Pedder, from Portsmouth.

With a time of 62.56secs, the York star was fourth fastest in the heats behind Jackson, who managed a qualifying time of 61.0secs, Pedder and Birmingham's Georgina Lee.

However, the former York City Baths Club swimmer remained confident of making the Australia-bound squad.

She said: "I used the heats just to get in their and swim with the idea of taking things on from there when the real test begins. Things are working out well and I expect to go faster each time.

"There are some pretty good kids around but I can't control what other people do, just what I do myself, and I'm still confident. I'll just have to make sure they finish behind me!"

She added: "I swam a similar time (62.55secs) in the Scottish Nationals heats and I went on to win that."

As regards setting a new personal best, she said: "It's going to be tough as the qualifying times that have been set are faster than I've gone before. But I don't think they are out of my reach.

"I will have to do a personal best to qualify but I don't believe that will be too much of a problem. I should be able to find it from somewhere."

Despite the upheaval following the controversial sacking of her coach and husband, Paddy Garratt, by York City Baths Club earlier this year, and her resulting switch to rival club Kingston Upon Hull, Foot was feeling ready.

"Preparations have gone really well, with everything geared towards this week." she said.

Foot will also be competing on Sunday in the national championships 50m butterfly, an event in which she broke the British record in May, improving her own personal best by 0.67secs. This is not an Olympic event, however, and thus not an Olympic trial.