However, Britain’s first fighter to win Olympic gold in the heaviest weight category has not fought since, despite hints on social media that he would resume his career.

“My boxing career has come to an end,” said the 43-year-old in a statement on his official website. “I am no longer a professional boxer.”

Harrison admitted that his decision has been prompted by research into head injuries he has suffered as a result of the punishing blows he took during his 38-bout professional career.

He added: “I looked at the latest research into concussions and Traumatic Brain Injuries (TBI). After years of denial and sticking to my guns, I’m finally getting out of my own way. As tough as it is to say this...it’s time to stop.

“I’ve suffered a few TBIs and will have to work hard to reverse some of the effects taking punches to the head has brought about to my overall health.

“I have vision problems, vestibular injuries that leads to balance disturbances, and have bouts of serious irritability and moodiness that comes with TBI recovery.”

Harrison did not translate his standout amateur career into success in the paid ranks – although he captured the European heavyweight title and fought fellow Londoner David Haye for a world title in 2010, when he was stopped inside three rounds.

Harrison, who was most recently on the latest version of Celebrity Big Brother, retires with a record of 31 wins and seven defeats.