Sketch: What Vince Cable could teach Labour Chuka Umunna, the children's ringleader, pulled out his pea-shooter and took aim. "May I congratulate the Business Secretary on his leaked letter," he began, with an air of mock-angelic innocence. "When [the "frankly rather piecemeal" quote] was put to the Prime Minister, he said the Business Secretary was wrong. I think it's grossly unfair that the Prime Minister should be allowed the last word. Could I ask the Business Secretary to explain why the Prime Minister is mistaken? Labour's business spokesman has a knack for smooth, serpentine irony, and this was a typically artful question, inviting Dr Cable to either condemn David Cameron or condemn himself. Dr Cable weighed up his options and decided to condemn someone else instead. His letter had been leaked, he said, by a Government department other than his. For some reason he neglected to identify this department. The official Number 10 website lists no Ministry of Undermining the Government from Within, so we'll just have to go on guessing. At any rate, continued Dr Cable defiantly, the leak had given him "excellent publicity," and his letter made "a very strong case which my colleagues in government share." Some of those colleagues may feel that the only strong case the letter made was the case for Dr Cable's dismissal. Some business leaders, too, come to that. About his plans for executive pay Dr Cable said little, other than that they will "hopefully have [a] moderating effect." The Business Secretary is often painted as stubborn and glum, and it's true that in the Commons he exudes about as much joie de vivre as a Dickensian headmaster. All the same, he can be entertaining to watch. With his sharp beak and stiff, jerky movements, he looks rather like an elderly woodpecker. A woodpecker that, now and again, seems to take particular satisfaction in peck-peck-pecking away at the Coalition. It's an intriguing sight - or, if you prefer, a compelling vision.