Great North Run founder Sir Brendan Foster praises the 'steely determination' of fellow runner Sir Mo Farah after childhood trafficking revelations

According to a BBC documentary, the gold medal winner was brought to the UK illegally as a child and forced to work as a domestic servant.

Born Hussein Abdi Kahin in Somaliland, north of Somalia, when he was just four years old his father was killed in the country’s civil war.

The death tore his family apart and he was later separated from his mother and trafficked to London under the name of another child - Mohamed Farah.

“I’m absolutely staggered really because I thought I knew the Mo Farah story and I thought I knew Mo Farah really well. I’ve known him for more than 20 years, since he was a young kid,” Sir Brendan, who founded the Great North Run and which is set to return to South Shields in September, told BBC Radio Four’s Today programme.

“You just have to feel so sorry for the man.

"And then when you think about it, the Mo Farah story is a fantastic story itself. But then when you see, when you realise what was behind the story, it’s a Hollywood movie now.

“And you don’t know whether it’s a sad Hollywood movie, or it’s a happy Hollywood movie.

"But it’s a great story and he’s a great man and you know, he hasn’t lied to anybody but imagine having to bury that, live with that story that he’s going to tell us probably when we watch it on TV. But it’s an amazing, successful story of someone overcoming adversity.”

Sir Brendan hailed Sir Mo’s “steely determination” in his life, adding he had been “absolutely staggered” by the details unearthed in the BBC’s documentary, released this week.

Sir Mo claimed he thought he was going to Europe to live with relatives, but recalled “not great memories” of his childhood in Hounslow, in London, where he was not treated as part of the family.

Instead, he said he was made to look after children in the house “shower them, cook for them, clean for them” and told by the woman who had brought him to the country: “If you ever want to see your family again, don’t say anything. If you say anything, they will take you away.”

Asked if he had ever seen any hint of the pain that was behind Sir Mo’s well-known grins, Sire Brendan said: “No, I just saw the grins and the silly behaviour and the way he laughed so easily.

“But when you think about it, if you think about the darkness that was in there, and behind this story, it is amazing that he came out – first of all with the light-hearted personality that he has, and then secondly, somewhere in there, the steely determination.”

Sir Mo has attended several previous Great North Runs and named the event among his favourites to compete in.

The Real Mo Farah is due to be broadcast on BBC One at 9pm on Wednesday, July 13, and is available to watch now on BBC iPlayer.