London 2012 Olympics: Snubbed Marilyn Okoro drops quit threat to join 4x400m relay squad Okoro, who is ranked No 1 in Britain this year over two laps, told UK Athletics head coach Charles van Commenee last week that she would be retiring from athletics after she failed to gain selection in her specialist event, despite being one of six athletes named in the relay squad. She was one of four athletes with multiple 'A" qualifying standards who missed out on 800m selection after the selectors took the controversial decision to choose just one 'B" qualified runner - Scotswoman Lynsey Sharp. Okoro, Emma Jackson and Jemma Simpson all appealed against the decision but their challenges were rejected on Friday. But Okoro, 27, has now backed down over her threat to walk away from the sport and used her Twitter page on Sunday to announce that she would be taking up her place in Britain's 78-strong athletics squad. She said: "I may have lost my appeal to run my 800 but I'm thankful to be on my way to my second Olympics Games." The announcement follows a successful couple of days on the track for the London-based athlete, who bettered Dame Kelly Holmes" UK record over the rarely run 600m distance when she clocked 1min 24.36sec in Liege on Thursday night. She also set a season's best 400m time of 52.67sec when she finished second behind GB team-mate Shana Cox in Heusden, Belgium, on Saturday night. Cox, Christine Ohuruogu and 400m hurdles specialist Perri Shakes-Drayton are likely to be first-choice selections for the 4x400m relay squad in London, leaving Okoro to battle it out for the final berth with Lee McConnell, Nicola Sanders, Emily Diamond and hurdler Eilidh Child. Meanwhile, world heptathlon silver medallist Jessica Ennis competed for the last time before the Olympics at Loughborough on Saturday, recording a long jump of 6.21 metres and a javelin throw of 44.73m. "I've done all I can do," said Ennis.