1) David Cameron is likely to open with a conciliatory tone in an attempt to placate worries about the basis for war among undecided Labour MPs. He is expected to steer clear of partisan swipes at Jeremy Corbyn after he urged Tory rebels not to vote on the same side as “terrorist sympathisers”.
2) It is a very unusual format but Corbyn will speak first for Labour to make the case against airstrikes and Hilary Benn will be closing to put the arguments in favour of bombing. It gives the Labour leader a headstart, making sure his MPs have time to mull over his words. But Benn has the last say, just before voting time at near 10pm.
3) There will be a lot of serious questions from MPs about the intelligence claim that there are 70,000 moderate rebel troops in Syria who can hold territory vacated by the bombing of Isis. This seems to be the weakest link in Cameron’s case. The waverers will be seeking genuine reassurance and those against will use it as evidence that the government has presented a dodgy dossier.
4) Labour MPs are likely to make angry points about Cameron’s insult to their leader, regardless of which way they are going to vote in the debate. In some ways, it will make it more difficult for them to walk through the voting lobby with a prime minister who has made such a slight on Corbyn. But it also gives the pro-airstrikes MPs an opportunity to denigrate Cameron in their speeches so they do not come across as completely on board with the Tories.
5) Some Labour MPs will be trying to read the mood of the room before deciding which way to vote. A large rebellion against Corbyn would give them cover, but a small one would mark them out as possible targets for those activists who want to get rid of disloyal Labour MPs.
6) A similar game will be happening on a lesser scale in the Tories but with promotions and patronage at stake. Those planning to vote against are mostly well known as veteran rebels. The most influential of the sceptic camp is probably Dr Julian Lewis, the Commons defence committee chairman, whose contribution could sway undecideds his way.
7) Some passionate oratory on all sides is guaranteed. The House of Commons is usually at its best debating matters of grave seriousness. There are likely to be heartfelt speeches against extending the bombing by Corbyn, Diane Abbott, Angus Robertson in the SNP, the Greens’ Caroline Lucas and rebel Tories such as David Davis. Equally fervent interventions in favour are likely from Cameron, and Labour figures like Mary Creagh, Alan Johnson and Hilary Benn.
8) At some point, prominent undecideds or unknowns will have to make clear their views. People will be closing watching the facial expressions of Andy Burnham, Yvette Cooper, and Harriet Harman for clues about their voting intentions.
9) At 10-and-a-half hours it is a very, very long time for a debate. The press gallery will be keeping a watchful eye out for anyone seen to be nodding off or playing Candy Crush at the back.
10) Despite the length, there will still be jostling for time to speak. Everyone will want to make sure their opinions are heard on such a weighty subject, so while it is unlikely to be rowdy, the role of the Speaker will be to stop MPs pontificating for too long.
