• Surprise announcement follows win in 3,000m at Birmingham grand prix • Briton had been expected still to compete for country in marathons

Mo Farah says he has competed for the last time in a British vest after delighting his home crowd with victory over 3,000m in the Birmingham grand prix. The 34‑year‑old made the surprise announcement after handing his GB vest to his team-mate Andy Butchart after crossing the line.

“It’s been amazing,” he said. “It’s been incredible. But I won’t be competing for Great Britain again. In terms of major championships, I won’t be taking part.

“That was my message for Andy: ‘This is me done. Take over from me and just inspire them. See what hard work is about and what it takes to be a champion.’”

Farah, who was also racing on Sunday for the last time on a British track, will next travel to Zurich to race over 5,000m on Thursday before heading to the Great North Run in early September. He is then expected to sign a lucrative one- or two‑year deal with the London marathon.

Previously Farah had hinted that he might be amenable to running the 26.2-mile distance at a major championships, either at the world championships in Doha in 2019 or the Tokyo Olympics in 2020. However, he admitted on Sunday that he had changed his thinking.

“It feels a bit sad,” he said. “All I ever wanted to do as an athlete is run for Great Britain. I remember when I did the mini marathon as a kid, I got interviewed and asked what I wanted to do, I said I want to run for Great Britain. To have achieved what I have achieved has been incredible.”

Facebook Twitter Pinterest Mo Farah takes off his Team GB vest after his Birmingham grand prix victory. Photograph: Tim Williams/Action Plus via Getty Images

When pressed, Farah said he would consider running in Tokyo only if he found that he was indisputably best in the world over 26.2 miles – which, given his best of 2hr 08min 21sec is more than five minutes behind the world record, seems a tall order.

“If I am the best at the marathon, I might compete,” he said, although his body language suggested otherwise. “It depends. But it’s going to take me at least two or three marathons to get it right, to learn from it. It’s not easy.”

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Farah was also asked about photographs on the running site Let’s Run which appeared to suggest that he was still training with Nike Oregon Project athletes and his coach, Alberto Salazar – who remains the subject of an investigation by the United States Anti-Doping Agency – more than he was letting on.

“I answered most of the questions last week. I’m done,” he replied. “This is about competing here, doing well and enjoying myself, being myself and normal.”

He was more expansive when asked if reports that he had fallen out with British Athletics’ head of endurance, Barry Fudge, were true. “Where did you get that from? Barry is still my mate, still hangs out, is still my right-hand man. He is still part of the endurance camp and is always there. He was in the training camp in Font Romeu, the last phase.”