Sir Mo Farah admitted his quest for double World Championship gold will be tough as he looks for the fairytale farewell.

The four-time Olympic champion goes for glory in the 5,000 metres while Jamaica’s sprint king Usain Bolt will also bow out of competition after the 4x100m relay in London on Saturday.

Farah, who races at 8.20pm, is wary of the competition – which includes Kenyan-born American Paul Chelimo who came second behind him in the 5,000m at the Rio Olympics last year.

His 10,000m triumph last weekend remains Great Britain’s only medal of the championships but Farah insisted he is not guaranteed another victory.

“I want to leave on a high because that’s the perfect note. But it isn’t going to be easy in the 5k. It’s going to be tough for me. There are a lot more guys,” he said.

“There’s a lot more decisions to be made in a shorter race. In the 10k you’ve got 25 laps so you can relax a little bit if you’re further back to make that decision and work around.

“In the 5k, if you’re not there at a certain point, or if someone’s going to do something and you’re not there, that’s it – it’s gone.”

Farah won double Olympic gold in the 5,000m and 10,000m in London in 2012 while he has also won six world titles and five European crowns.

Sir Mo Farah's golden moments
(PA graphics)

He will end his track career at the Diamond League final in Zurich on August 24 after racing at the Diamond League meet in Birmingham next Sunday.

“To have achieved what I have achieved has been incredible. I don’t think there’s enough words to explain the journey and everything,” he said. “But you have to appreciate what you have and do the best that I can. That’s what I was taught in my early years. Appreciate it.

“Yeah it is emotional but it has been a long career. You guys have seen me since I was a child, running around, going to the English Schools. To come this far has been incredible.”

Bolt won bronze in the 100 metres last Saturday, finishing behind Americans Justin Gatlin and Christian Coleman to miss out on a 12th world title.

But he is out to defend a relay title he has won in the past four championships and Bolt has already insisted he has no regrets ahead of his last race, as long as Jamaica qualify, which is scheduled for 9.50pm.

“No matter what happened this season I was going to come out and do my best,” he said after his 100m bronze. “I did it for the fans, they really wanted me to do one more season.”