Cavendish has twice finished as runner-up at Six Day London with Bradley Wiggins and then Peter Kennaugh alongside him but is desperate to triumph this time around.
Five teams came into the penultimate night of racing 'on the lead lap' with Elia Viviani and Simone Consonni's points total putting them at the top of the standings despite a number of Cavendish triumphs over his Italian rival.
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But the Italians gave up a lap in the very first race of the day, a 20-minute madison, allowing Cavendish and Doull to move joint-top of the General Classification.
And Viviani, the man on the golden bike, as beaten once again as for the second time this week, the two star sprinters were the only men remaining at the end of the team elimination.
On Thursday, Viviani had led it out and Cavendish had beaten him over the top - this time the roles were reversed but the result was exactly the same.
And it was not the only time that one of Britain's best successful ever sprinters would beat his biggest rival for the Six Day title as Cavendish found a way to win the final race of the night.
The Italians had joined forces with German world champions Theo Reinhardt and Max Beyer in an attempt to steal the win, only for Doull to latch on.
With Cavendish resting high on the track, the Welshman produced an unbelievable turn before catapulting his partner into action on the very last lap.
The rest was classic Cavendish and he beat Viviani by more than a bike length having been effectively standing still 250 metres before.
Cavendish powers past Viviani in the Madison Chase
They head into the final day of action with only the Germans on the same number of laps and all the form in their favour.
GB have dominated the women's event, with Katie Archibald and Neah Evans leading the way ahead of the final day of action.
However, Elinor Barker and Laura Kenny, who won the team elimination on Saturday evening, are second just 14 points shy of their countrywomen with it all to play for on the final night of competition in London, with the scratch race and a 20km Final Chase to come on Sunday.
Barker, Kenny seal team elimination win after Evans and Archibald error
Emily Nelson and Manon Lloyd sit third on 104 points,
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GB's Backstedt beats Schmid to take stunning gold in women’s junior road race