And those few places that remain up for grabs have brought into sharper focus next week's European Championships in Finland, which have now assumed a huge degree of importance for many as one of the final opportunities to earn a late invitation to the capital.
Equally, however, this weekend's trials at Birmingham's Alexander Stadium could also be decisive for a select few. Lynsey Sharp took her first UK 800 metres title in some style at the event yesterday, but is among those still living in a world of uncertainty. The 21-year-old from Edinburgh produced a searing burst down the home straight to claim victory as rankings leader Marilyn Okoro paid a painful price for a suicidal early pace.
Sharp's seasonal best of 2:00.65 is more than a second outside the A standard laid down for the Games. Now her mission becomes simple. If she runs under 1 minute and 59 seconds within four weeks, she will emulate her father Cameron as an Olympian. If not, the selectors must make a call. "I still have it in me to get the time," she said. "I wasn't thinking about the time, just about the racing."
Glasgow's Lee McConnell will assuredly go to her third Olympics as a member of Great Britain's relay squad. Whether she has an individual invitation remains undecided. She, too, will head for Helsinki with a need for speed after coming third in the 400 metres, behind Olympic champion Christine Ohuruogu and Shana Cox who both solidified their spots on Team GB.
McConnell said: "I have to have a word with the head coach and selectors and see what's required to get into the team and that probably dictates what I have to do out there."
Those in possession of the A standard, who also came in the top two here, can already clear some space in their wardrobe for the gargantuan array of free kit that comes with membership of what the marketing men are calling Our Greatest Team. For the likes of world champion Dai Greene over 400 metres hurdles, and Sophie Hitchon in the hammer, victories ensured the formalities were completed.
Dwain Chambers was under pressure to find form and a performance after the legalities of his eligibility were decided by the lawyers at the Court of Arbitration for Sport. Fourth in 2000 in Sydney, even reaching the final in London would be unexpected, but he may get his shot after holding off the prodigious Adam Gemili, 16 years his junior, in a season's best of 10.25 seconds.
Punching the air with raw emotion after he crossed the line, he still must go seven-hundredths of a second faster to guarantee a spot. "It's been a long journey," he acknowledged. "I don't want to let my guard down yet. I've still got to get that qualifying time and I'd rather get it from merit than the selectors giving me an opportunity."
Jessica Ennis will be there, of course, but she is using this weekend as a sharpener. The heptathlon hopeful leapt a season's best of 1.89m to win the high jump and then ran 12.92 seconds in the 100m hurdles to see off domestic foe Tiffany Porter. "To win it was brilliant," said Ennis, who will do the 200m and long jump today. "To know that I'm in good shape and things are moving forward is great."
Eilidh Child was the fastest qualifier for the 400 metres hurdles final, running 55.83 seconds to claim a seventh consecutive victory. It was yet another mature performance but, in tandem with her coach, Malcolm Arnold, she is still making tweaks.
"That was a test to see if I could do that stride pattern we planned," she said. "I don't think that took too much out of me, but you can never go too slowly when you're trying to get your stride pattern right."
The fate of fellow Commonwealth medallist Steph Twell is up in the air. Passing on the 1500 metres, she pulled out of today's 5000m with a foot injury, the sole event in which she has the qualifying standard.
In the absence of Twell and world silver medallist Hannah England, Laura Weightman will start as favourite in this afternoon's final. Lisa Dobriskey, returning after injury, progressed in the quickest time, while Dundee-based teen Laura Muir won an earlier heat in a best of 4:17.81.
Andy Baddeley claimed the men's 1500m title in the absence of Mo Farah. The world champion withdrew after winning his heat on Friday, confirming that he will defend his European 5000m title in Helsinki next weekend.
Lasswade's Guy Learmonth will not be there after being omitted from Britain's squad. Victorious in his 800m heat, he admits he is out to make a point to the selectors. "I respect UK Athletics' decision," he said. "But it makes me hungrier and more determined go quicker."
Highlander Mark Dry will head to the Europeans, but will look to turn the screw on his hammer rival Alex Smith today in their duel for Olympic selection. The Scot is the only Briton with a qualifying mark and admits he'd be heartbroken to miss out. Eilish McColgan, already possessing an A standard, will chase her first senior UK title in the 3000m steeplechase.
Yet arguably the performance of the day was from a runner-up. Roald Bradstock, aged 50, came second in the javelin – 18 years after coming seventh at the 1984 Olympics in Los Angeles.
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