The actor first attempted the huge feat in South Africa in 2012 to pay tribute to the country's former president and the 27 years Mandela spent in prison as he fought against apartheid, but health concerns and tough running conditions forced him to bow out of the mission after just four races.
In March (13), Izzard revealed he was hoping 2014 would be the year he achieved the charity challenge and now the star admits Mandela's death earlier this month (Dec13) has given him extra inspiration to reach his goal.
The 51 year old tells BBC Radio 5 Live, "I'm going back. Nelson Mandela said, 'Don't just me by my successes, judge me by the number of times I failed and got back up again. I'll just keep doing it until I win...
"I'm trying to just be a student of Nelson Mandela and just be influenced by him."
Izzard reaffirmed his marathon pledge on Monday (16Dec13), just a day after the civil rights icon was laid to rest in his childhood village of Qunu.