Harriet Harman’s impressive PMQs form continues unabated. Post-election David Cameron may be in too strong a position to really struggle at the weekly bouts, but where previous Labour leaders would have wilted, Harman comes away with what, on balance, we can probably call a victory.

She used her first questions to talk about the terrorists attack in Tunisia last week, and ask the PM about what steps the Government is taking to help victims and their families.

As always, there are no political points to be scored on a topic like this. The exchange was civil, measured and informative. Both leaders rose to the occasion of putting aside the politics and discussing what practical measures could be taken.

Moving onto the subject of Heathrow expansion was where Cameron started to look a little shakier. Harman may have surprised him by hardening Labour’s stance on the issue, and taking a very clear pro-expansion line, supporting the recommendations of the Davies Report published this morning.

While it is true that Labour are not completely unified on the issue, the problems posed to the Tories are much greater. Boris Johnson has long been a vocal opponent of Heathrow expansion, and will have no hesitation causing trouble for Cameron from the backbenches. With Zac Goldsmith likely to be the Tory candidate for London Mayor, Cameron’s headache is even worse – he promises to cause a by-election if the Conservatives back the plan.

Cameron’s solution? Kick the issue, once again, into the long grass, and hope things are easier the next time he has to deal with it. He now says that he will take a position by “the end of the year”, where he had previously planned to do so by September.

Eventually he’s going to run out of grass. If he then supports the Heathrow plan, he’ll face a mutiny of which Boris and Goldsmith are merely the most well known. If he comes out against it, he will face accusations that he has lost control, and Boris is already running the show – the next Labour leader can say Cameron is putting Tory unity above the national interest.

Harman handled both situations deftly today, and her take on the latter will pay dividends for Labour down the line.

The SNP’s Angus Robertson, who now has two questions each week, is also proving himself adept at his higher-profile task. However, there were problems with the Nationalists PMQs role today.

Firstly, the SNP had five questions in the half hour session today, including Robertson’s two. All five were on the same topic: Cameron’s plans for English Votes for English Laws. Not only that, they were essentially the same question. This doesn’t help the increasing appearance that SNP’s, far from the independently-minded mavericks we were promised, are at the beck and call of their party HQ. It’s also quite repetitive. The PM had given a reasonable answer on the first request – it just wasn’t the answer the Scottish Nationalists were interested in.

The second problem for them is a little more subtle. It is just sitting there, silently waiting, in a seat that will ensure maximum television exposure. Seen but not heard.