In round 12 Williams connected with a series of shorter punches thrown from inside the looping arc of Skelton's own wild swings; suddenly the fight looked over.
However, Skelton is an expert at survival, having made a living on the savage K1 circuit in the Far East, and he had enough sense to throw Williams to the canvas and gain a few seconds of respite.
The damage had finally been done, and for the remainder of the final round, Skelton was mostly oblivious to his surroundings and clearly just one clean punch from a concussive defeat. Williams was exhausted, a now familiar state for the veteran Brixton heavyweight, and missed his opportunity to win convincingly. At the last bell the pair embraced in a bloody and sweaty 40-stone mass.
The three judges delivered their split verdict, and for the second time in three months Williams left the ring at the ExCel with a controversial decision win.
Last December he beat Audley Harrison and nobody wanted a rematch, but Saturday's gruelling encounter will almost certainly be fought again. In theory, Saturday's winner will fight the World Boxing Association champion, Nikolai Valuev of Russia, later this year, but that fight is unlikely to get in the way of another instalment of Saturday's encounter.
Williams, still only 32, admitted after the fight that Skelton had been far more awkward and much stronger than he expected. In other words, Williams once again managed to get his preparation wrong, having entered the ring against Harrison in dreadful physical condition.
As expected, Amir Khan won for the sixth time when he stopped Norwich's Jackson Williams in the third round.