She needn't have worried.
Red Ed was in full "serious and sober" mode, being a good comrade and, for a change, backing up the PM. The issue was the Ukraine, serious and sober stuff, which meant that the political cudgels for once were kept unused.
But the only true moment of party political nose-tweaking came when Labour's former Foreign Secretary, the lawyerly Jack Straw, raised the somewhat obscure issue of the Trans-Pennine Express.
The MP for Blackburn conjured up a level of indignation when he informed colleagues that the said train service, which serves the north of England, was moving one in eight of its trains to, shock horror, Chiltern Railways for the "greater comfort and convenience of commuters in the south of England".
At this point, Tory MPs began to titter, so much so that the right honourable gentleman could not continue and the Speaker had to intervene. The source of their merriment appeared to be that Mr S has a home, er, in the Cotswolds and, not just that, but in the very constituency of one David Cameron.
The ex-Secretary of State, when he got back to his feet, hit back, saying: "I just say to members opposite, this may be a laughing matter for them, it is certainly not a laughing matter for people in the north of England." Mr Straw was in such a huff he continued on speaking even after the microphone relaying his voice was turned off.
Blue Dave was smirking all the way through and when he got to his feet to respond we all knew the reason why.
"I hope he won't find it too cheeky if I point out the line both he and I use, of course, the Cotwolds line and Charlbury railway station, has also received a lot of extra investment under this Government. He now enjoys a double track line when he makes his journey from my constituency into London."
As the Tories cheered, good old Jack couldn't help raising a wry smile himself.