Mo Farah's return to competitive action at the London 10,000 saw him finish as runner-up to Ellis Cross in Monday's Championship race.
The four-time Olympic gold medallist was making his comeback in the event after his failure to qualify for the Tokyo 2020 Olympics and was aiming to build on his seven previous victories at the London 10k.
However, Farah was unable to keep pace with Aldershot & Farnham District's Cross during the event and crossed the line in second place with a time of 28 minutes 44 seconds - a whole minute off the course record he previously set back in 2010.
Cross took the crown with a time of 28:40, and Farah left his future in competitive athletics open to debate after claiming that he "is not young anymore" after his second-placed finish.
"I love being back at home in London, this is where it began in my early years and today was tough, but it's really important to test your body and see where you are," Farah told BBC Sport after the race.
"I did put in some good blocks of training together but it's been so long - nine months - since my last race. I love what I do and I've had a long career, but at the same time there are a lot of youngsters coming through, which is nice to see.
"Your body has to be ready, you have to be in the right frame of mind to be able to compete with the guys, and like I said today was a tough day.
"Ellis did really well to beat me, at the minute I don't really know where I am now. I'm taking it race by race, as I said I'm not young anymore!"
Meanwhile, Cross revelled in his triumph against Farah in the capital, adding: "I can't believe it, I didn't really believe it until about 20 metres away from the finish, I thought he was going to outkick me!
"I can't explain the feeling, it's overwhelming to do it and I'm absolutely delighted with the run and the performance. I wasn't really focusing on the time today, I just wanted to go and have a hard run-out.
"I've beaten someone who is like an idol to me and I've beaten him over his prime distance. Everyone's cheering Mo on, I've just got a number on, no one knows who I am so I don't think I followed the script today!"
Mo Aadan placed third in the men's race behind Farah and Cross, while Eilish McColgan finished just two seconds off Paula Radcliffe's British 10k record to win the women's event with 30:23 and set a new Scottish record. body check tags ::