The wheelchair racer, who won four Paralympic golds at London 2012, retired from international competition last year, shortly after being accused of throwing a race at the Rio 2016 Games.

In an emotional interview with BBC Sport, the 39-year-old admitted the dispute with a coach led to a period of deep depression, but having sought counselling he is now in a “positive mind set”.

“I was very bitter about what happened in Rio,” he said.

Following the Games, during which he missed the birth of his fourth child, Weir split with his partner and moved out of his family home.

“I wanted to jack life in, to be honest,” he said.

“I had had enough of everything."

Weir added: I’d never have done it because of my children.

“But there were some dark days when I didn’t want to be here, to be honest.

As a result the 39-year-old sought counselling and now says nothing can get in his way.

“I’m going to make sure I get to Tokyo, put the Great Britain vest on and feel very proud to wear it like I did in 1996 [his Paralympic debut],” he said.

“I said I’d never wear the vest again.

“I’m going back on my word, but if I can still deliver and win a medal like I think I can, then why not?”

Weir took part in, and won, the London marathon last April and also triumphed in the Great North Run last Sunday (September 9).

"I feel like the old Dave again," he said.

"I've had a lot of time away thinking about what I want to do,

"I've probably got five years maximum left in my career. 

"I'm nearly 40. 

"But I'm just really enjoying it again, really enjoying the sport, really enjoying life, so that's what has made me do a U-turn."