After years of waiting and training, D-Day finally arrived for Britain's athletes today with the first day of the Olympic trials set to get under way in Birmingham.
On the face of it the equation is simple - finish in the top two in your event in the trials while in possession of a current 'A' standard and a place on the team for London 2012 is yours.
But while the likes of Jessica Ennis and world champion Mo Farah are already guaranteed selection, matters are not so clear cut for many others - especially in the men's 100 metres, which starts with this evening's heats.
Only two men - James Dasaolu and teenager Adam Gemili - have run under the 'A' standard of 10.18 seconds, but neither of those can be certain of finishing in the top two tomorrow to get the job done.
Dwain Chambers had been expected to make the most of the fact that the British Olympic Association's lifetime ban on drugs cheats has been overturned, but the veteran has so far failed to grasp his opportunity.
The 34-year-old's best time of 2012 remains the 10.28secs he clocked when finishing second behind Usain Bolt in Ostrava in May, while a poor weather forecast for the weekend will not boost his chances of securing the qualifying time.
That could mean being forced to chase the time at the following week's European Championships in Helsinki, even though UK Athletics head coach Charles van Commenee admits that is not an ideal scenario with the London Games just a few weeks away.
Along with the first two athletes across the line in Birmingham, the selectors do have another discretionary place at their disposal, but Chambers would love to remove all doubt this weekend.
Elsewhere today, world 400m hurdles champion Dai Greene will be looking to put a disappointing start to the season behind him with a convincing performance in a high-quality event.
Four years ago Britain did not send anyone to Beijing in the event, but now five athletes have achieved the 'A' standard with Greene's training partner Jack Green, Nathan Woodward, Rick Yates and Rhys Williams all battling it out for selection.
In the women's 800m, the withdrawal of Jenny Meadows due to long-running injury problems leaves her in serious danger of missing out on the Games, with Marilyn Okoro and Emma Jackson favourites to gain the top two places. Jemma Simpson has a big point to prove after being dropped from Lottery funding.
But perhaps the best action of the opening day will barely feature British athletes at all, with Olympic champion Kenenisa Bekele and several other world-class African athletes set to dominate the 10,000m final.
Bekele has been plagued by injuries and remarkably still needs to impress his country's selectors, with his brother Tariku and compatriot Gebre Gebremariam showing better form so far in 2012.
Farah will contest the heats of the 1,500m to work on his finishing speed just before the 10,000m final, but is certain to be watching closely to see how Bekele responds to finishing well behind the Briton over 5,000m in Oregon recently.