Watching the recording of PMQs on BBC's Parliament channel last night I was struck by Brown's palpable diminution. As every one of Cameron's barbs struck home he tried desperately to rally, struggled with every rehearsed quip printed on his crib-notes. A couple of weeks ago he came up with quite a good riposte - the Tories are the 'do-nothing' party - but a week is a long time for political catch phrases. As Brown ensured he worked this into every reply, it sounded increasingly hollow. He was like the boy in the playground doing Jimmy Durante impressions when the rest of the school had moved on to Hancock.
Brown's uncertainty grew as he realised something was missing. No-one in the playground was laughing. His own benches should have raised a rousing cheer every time he thumped down his catch phrase, but all they managed were a few ragged grunts. His frustration grew visibly. The force had gone out of his punches. As he petulantly flung himself back down on his bench, it was clear that his authority was evaporating fast.
Cameron refrained from using this week's Tory quip - headless chicken - but you could hear it hanging in the air; the Labour benches were expecting it, Brown probably had at least three counter-quips carefully scripted for him in his folder, but it never came. Unspoken, it hung there. The glances from Brown's benches as their leader flailed about were telling. They said headless chicken.