Gordon Brown fails to tackle Killer Cable - the man with the withering wit.

9.40.25am UTC (GMT +0000) Thu 13th Dec 2007

Vince Cable has become Mr Brown's nemesis

After his devastating "Mr Bean" put down of the prime minister a couple of weeks ago, the stand-in Lib Dem leader's turn at Prime Minister's Questions has become one of the week's much-anticipated highlights. And this time he came up trumps with an off-the-cuff thunderbolt. The prime minister has his approach to David Cameron well worked out. It is to cast the Tory leader as a lightweight with no substance who would rather concentrate on gossip and personality than substance. But Mr Brown is still struggling to know how best to slap down Mr Cable, with whom he previously had a relatively friendly relationship.

So, when Mr Cable asked him which of the disasters to have battered the government over the past six months would haunt him most over his Christmas sprouts, Mr Brown tried a fresh, pre-prepared put down. Tongue firmly in cheek, he thanked Mr Cable for his contributions over the past few weeks and suggested that, at the current rate of leadership turnover in the party, he might be back in his stand-in role not long after the next Lib Dem leader has been elected.

Gordon Brown does not know how to combat Vince Cable

Killer Cable hardly hesitated: "Given his own position, he might not be wise to speculate about leadership elections." Gordon Brown was devastated and had no answer. He must be wishing for the Christmas holiday period to arrive and give him a break, at least from his new nemesis Vincent Cable.