Four-time Olympic champion Sir Mo Farah has disclosed he was brought into Britain illegally from Djibouti under the name of another child.

“The truth is I’m not who you think I am,” the 39-year-old Farah told the BBC in a documentary called The Real Mo Farah.

Farah, the first British track and field athlete to win four Olympic golds, said his children had motivated him to be truthful about his past.

“The real story is I was born in Somaliland, north of Somalia, as Hussein Abdi Kahin,” he told the BBC.

“Despite what I’ve said in the past, my parents never lived in the UK.

“When I was four my dad was killed in the civil war, you know as a family we were torn apart. I was separated from my mother, and I was brought into the UK illegally under the name of another child called Mohamed Farah.”

In the documentary, father-of-four Farah reveals he thought he was going to Europe to live with relatives. He recalls going through a British passport check under the guise of Mohamed at the age of nine, after travelling with a woman he didn’t previously know.

“I had all the contact details for my relative and once we got to her house, the lady took it off me and right in front of me ripped them up and put it in the bin and at that moment I knew I was in trouble,” he said.

The athlete returns to his childhood home in west London, recalling “not great memories”.

Rather than being treated as a family member, he had to do housework and childcare “if I wanted food in my mouth”. The woman told him: “If you ever want to see your family again, don’t say anything.”

“Often I would just lock myself in the bathroom and cry,” he says.

He initially wasn’t allowed to go to school. But eventually he started in year seven at a London college.

Farah eventually told his PE teacher Alan Watkinson the truth and moved to live with a friend’s mother. He stayed with the family for seven years.

Meanwhile, Mr Watkinson had noticed a transformation in Farah out on the athletics track.

“The only language he seemed to understand was the language of PE and sport,” he says.

Farah said the sport was a lifeline – “the only thing I could do to get away from this [living situation] was to get out and run”.

Farah’s lack of travel documents was revealed when he was invited to compete in Latvia.

Mr Watkinson helped him apply for British citizenship, which he described as a “long process”. Farah was eventually recognised as a British citizen in 2000.

“Family means everything to me and, you know, as a parent, you always teach your kids to be honest. But I feel like I’ve always had that private thing where I could never be me and tell what’s really happened,” he said.

“That’s the main reason in telling my story because I want to feel normal and … don’t feel like you’re holding on to something.”

The documentary ends with Farah speaking to the real Mohamed Farah, adding he will continue to go by the name he was given when he entered Britain.

-with AAP