While last week turned British politics into a new show called "The Clegg Factor", last night's clash brought things back to much more old-fashioned territory – that of party literature.
It all began when Gordon Brown mentioned that the Tories would drop a range of benefits for the elderly.
Who thought this was about young voters? Last night showed that the result is a grey area in more ways than volatile polls.
"You should be ashamed of yourself," Mr Cameron said to the PM. Labour's leaflets are "lies".
"I did not, authorise them," Mr Brown replied.
Little did he know that cheeky Wee Eck Salmond was sitting in a back studio holding one of those offending bits of paper from Kirkcaldy – yes, that is Mr Brown's constituency.
But since last week's live debate on ITV, Lib Dem leader Nick Clegg has looked like a man walking on air, the real question was how his opponents would deal with him on Sky.
As Mr Brown opened the proceedings, you could almost hear a voice in his head telling him: "Look at the camera, Gordon, be more like Nick, for God's sake don't say you agree with him… no, look at the camera."
At least he got in the line about it not being a TV popularity show. Ladbrokes had been offering good odds on Mr Brown saying "I agree, Nick" nine times, up on his seven from a week ago. We had our slips ready, but then: "I agree with Gordon."
What? Who said that? There was Mr Cameron looking serious and saying something about nuclear weapons. Must have been an aberration. Five minutes later Mr Cameron took a deep breath: "I never thought I would say this…" Hmmmm? "But I agree with Gordon."
Actually, it's becoming a habit, David. And just as Tories shouted "For God's sake, David!" somebody asked a question about the Pope.
Meanwhile, nobody seemed to agree with Nick. But, hold on, 35 minutes in: "I agree with Nick". Good old Gordon, he just couldn't help himself, although this was on a charge of Mr Cameron aligning himself with "nutters and homophobes" in Europe.
Mr Cameron shook his head sadly. "One of my allies was the party of the president of Poland who has just died," he said. "The other two have recently been praising him as a great patriot and statesman. So we'll have less about that." For once, he got his way. However, it did not stop Mr Clegg and him having an argument over who is better on European referendums.
Mr Salmond must have been screaming at the TV screen: "What about the Scottish referendum?"
But it was the Scot in the room who had the last, and in fact only, laugh. "They remind me of my two sons squabbling at bath-time," said Mr Brown.
Who reminded us that the weather's not so good north of the Border. Then he remembered strategy. Ah yes, don't be nice to Clegg. Don't agree with him.
"Get real, Nick", he boomed. That one was on Trident and the Lib Dems leaving Britain defenceless to nuclear-armed Iran and North Korea. "Get real, Nick", he added for good measure. Three times in one sentence. You never know, Mr Brown may have come up with another new range of T-shirts.