You could also try moving to Bhutan. The women's marathon athlete from Bhutan ran a slower than 4-hour marathon in Paris.
I saw this when I watched the Olympic slalom in 1980. I was astounded by how powerful Stenmark and Mahre were, something just simply not captured on TV. It was like, "Oh yeah, we are not actually competing in the same sport." But then came some of the last skiers from countries that have no tradition of skiing and I could have easily beaten the last ten athletes. Once again, it was like, "Oh yeah, we are not actually competing in the same sport."
So if they question is, "Could you make Team GB?" that is one question. If the question is, "Could you beat the last place athlete at some Olympic sport?" that would be a much different question.