WHILE the majority of Olympic sports have already selected their competitors for London 2012, UK Athletics have opted to keep their powder dry until the last possible moment.

This weekend, in Birmingham, that moment arrives. The UK Championships are doubling up as the Olympic trials, and over the course of the next two days, four years of toil and effort will be boiled down into one competition.

Get it right, and you're off to the biggest sporting event of your life. Get it wrong, and you're either at the mercy of the selectors or your dream is over.

In every discipline, a top-two finish will guarantee an Olympic place provided the person securing it has achieved the Olympic 'A' qualification criteria within a designated time frame.

So while an athlete like Teesside long jumper Chris Tomlinson can justifiably consider himself one of the two best competitors in the country, his past achievements will count for nothing if he flops this weekend and two other jumpers sail past the qualifying mark.

"I haven't been thinking about the Olympics in the past few weeks because, first and foremost, I have to qualify," said Tomlinson, whose long-jump tournament is one of the highlights of this afternoon's schedule. "That's the only thing that's important this weekend.

"I've got to come here and finish in the top two, it's as simple as that. As long as I do that, I can drive back down to London and say I've qualified for the Olympic Games. Then I can start thinking about the future."

No longer British number one after Greg Rutherford equalled his British record with a leap of 8.35m last month, a jump that is still the longest in the world this year, Tomlinson is also behind JJ Jegede in this season's rankings.

Injury ruled him out of the entire indoor season, and while he has gradually found his form in the last few outdoor competitions, he is yet to achieve the 'A' qualifying mark, something that piles further pressure onto his shoulders this weekend.

Rutherford's emergence as a genuine medal prospect has shifted Tomlinson out of the limelight, but the Middlesbrough-born jumper insists he is delighted to see his compatriot competing so strongly.

"It's absolutely brilliant for the sport in Britain," he said. "I've always said we need to have British athletes who are highly-ranked in the world going head-to-head winning Diamond League meetings and major championships. That's what we're getting in the long jump now.

"Greg is sitting there as the world leader at 8.35m - the same distance that I jumped last year. Hopefully, we can put on a good show this weekend, and apparently there's some major event happening in London later this year so hopefully we can put on a good show there too."

While Tomlinson cannot afford to take anything for granted this weekend, it will be a major surprise if Redcar race walker Jo Jackson does not book her place in the Olympic 20km walk tomorrow.

Jackson is firmly established as the British number one in her discipline having claimed a gold medal at the 2010 Commonwealth Games in New Delhi, and should confirm her participation in the Olympic walk, which will take in Pall Mall on the penultimate day of the Games.

The Cleveland walker finished 23rd in last year's World Championships in Daegu, and while she is reluctant to look too far into the future, she is confident of posting an improved performance on home soil.

"I normally keep my goals and aims to myself but in terms of London I think I'm capable of top eight," said Jackson.

"I've had some injury problems but if I'm fit and healthy that is achievable. It's an event where anything can happen because of the rules."

While Tomlinson and Jackson have competed in previous Olympics, a number of North-East athletes are hoping to make their Olympic debut in London.

Morpeth Harrier Laura Weightman has improved markedly over 1,500m this season, and having already secured the 'A' qualification mark, the 20-year-old, who is trained by Steve Cram, could surprise some of her more established middle-distance rivals.

"I've worked with her as coach for three years now and to be honest, at the back end of 2009 the Olympics seemed a long way away," said Cram. "But the London Games have been a massive inspiration for a lot of young athletes and she is a prime example. She has worked really hard and is really ready for this."

Chester-le-Street's Vicki Barr will hope to secure a 4x400m relay spot, while York's Richard Buck could claim an individual berth as well as a relay place.

Away from the North-East, attention will be focused on Dwain Chambers' attempts to qualify for the 100m following the BOA's forced relaxation of its lifetime ban for drug offenders earlier this year.

Jessica Ennis, Mo Farah, Dai Greene and Phillips Idowu are also in action, while the weekend concludes with Commonwealth gold medallist Andy Turner in a keenly-contested 110m hurdles.