[1] Mitchell made his professional debut for promoter Frank Warren on 17 July 2003, scoring a first-round knockout of Stevie Quinn.

On 10 December 2005, Mitchell stopped Mohammed Medjadji in six rounds to win the vacant IBF Inter-Continental super-featherweight title, his first regional championship.

At the end of the twelve-round, the judges scored the fight as a wide unanimous decision for Mitchell, handing him his 31st consecutive professional victory and the WBO Inter-Continental lightweight title.

[6] Another year of relative inactivity followed until 22 September 2012, when Mitchell faced WBO lightweight champion Ricky Burns for his first world title opportunity.

From 2013 to 2014, having switched promoters to Matchroom Sport and reunited with former trainer Tony Sims, Mitchell earned four wins in what proved to be a steady return to form.

On 31 May 2014, an unexpected stiff test came in the form of Ghislain Maduma, on the undercard to the rematch between Carl Froch and George Groves at Wembley Stadium.

In the fight against Maduma, Mitchell gave up an early lead on points and absorbed many clean punches from his highly aggressive opponent.

He told Sky Sports, "I've had a good think about it over the last week and I'm happily retired now… I've been doing this 22 years and it's time to call it a day and start a new chapter in my life.