12:33 - The session winds down with a final question on military spending. Cameron jumps on national security questions - it's his attack line against Corbyn. But he does so without too much Punch-and-Judy. Corbyn was right - he did promise that himself and then admitted that he failed to deliver. Maybe he actually believes in it. OK, well that's it from us for this week. We'll have a verdict from Adam up in a moment.
12:31 - A Tory MP tries to sneak a national anthem jibe into a question on school funding. Tellingly, Cameron ignores it.
12:28 - Trident is raised. Cameron says defence is the most important issue for a government and he summarises 2% GDP defence spending, Trident and Nato and says it's "regrettable" Labour is turning away from these policies. A low cheer from the Tory benches. But they are nothing like as frenzied as could have been expected. Nigel Dodds, DUP leader, who looks so angry he might cry, attacks McDonnell, the new shadow chancellor, for his comments on the IRA. Cameron gives him a warm reception. "The terrorism we faced was wrong, it was unjustifiable. People who seek to justify it should be ashamed of themselves." Damaging moment for Labour there, which will enhance nervousness about McDonnell's appointment
12:27 - Interesting exchange between Cameron and Angus Robertson, SNP Westminster leader. Cameron initially went in hard, then was reminded this was not the way of the new-style PMQs. "This is going to take some getting used to", Cameron says "but let me answer him calmly." That was an interesting moment. It gave the impression of Cameron was following Corbyn's lead.
12:26 - So overall, given the extent of negativity around him and how easily he could have fallen on his face here, I would give it to Corbyn. Final score: Cameron: 1 Corbyn: 2.
12:24 - For his part, Cameron was smart in being very courteous to Corbyn. He can afford to let the press and, let's face it, the Labour party, mercilessly attack him. It's sensible for him to be very polite in these exchanges. Cameron got exactly the right tone.
12:19 - On the other hand, that public questions strategy will never deliver a victory at PMQs. They're just too scattered. It's like taking a tour around politics. But without Corbyn being able to deliver follow-up questions in response to what's said, he can't press Cameron on details. The great advantage of PMQs is that it allows follow up questions. Any politician worth their salt can bat away a single question. It's follow up questions which pin you down. Corbyn's strategy of public questions could work - but he will need to be less strapped down to it and give himself more room to manoeuvre.
12:17 - There's murmuring everywhere, but no jubilation on either side. I would say overall that's a victory for Corbyn. After most Ed Miliband PMQs the Tories were ecstatic and very noisy. And given the press attacks Corbyn has faced ahead of today, many expected it to be a car crash. Instead it was... different. At the least, he has neutralised what could have been a challenging moment for him. And he conducted himself well - he didn't display any nerves. He came across as principled and moderate and genuine. There was a lot to be positive about here.
12:15 - Cameron: "I say we need to do more as a country to tackle mental health." He says mental health beds are important, as Corbyn said, but GP visits are too. He says it's about resources, the way the NHS works and public attitudes to mental health. And that's it. There is quiet in the Chamber. I think MPs literally don't know what to make of it.
12:12 - Cameron says working should always pay more than not working. "Many people don't have that choice," he says, sternly. The tone Corbyn is using here is oddly effective, I think, even if this public questions tactic is flawed. Gail asks about mental health services. Cameron says the two men can work together on this. He accepts the need for action. "We've made the commitment on the Stevens plan for an extra £8 billion to the NHS in this parliament." He then says "we can't have a strong NHS unless we have a strong economy." The standard Labour attack follows. Corbyn's last question now I think. "If I can take the PM back to the issue of mental health," he says. "The crisis is a very serious one." The next question is from Angela, a mental health professional. She lists some of the inadequacies of the system. "What does the PM say to Angela, or people going through a mental health crisis, and want to know that we take seriously their conditions?"
12:10 - Corbyn cites Claire. How will changing thresholds of tax credits help children or families. They say their income will plummet. How is it fair? "The country has to live within its means," Cameron replies. "What we're doing is moving from an income of low wages and high welfare, to high wages and less welfare. Let us not go back to the days of unlimited welfare."
12:09 - There are complaints from Labour. "Sorry, I thought this was the new question time," Cameron says. "I'm not sure the message has got through." Corbyn's problem here is his reliance on public questions means he can't do follow up questions. So Cameron can reel off slogans ("causes of poverty") and stats and he gets off the hook.
12:07 - "What I would say to Steven..." Cameron says. There is a murmur of disapproval in the Commons. You can feel the bristle of discomfort at the fact people from outside the Chamber are asking questions. Corbyn is up again. He says the Commons voted through proposals on tax credits. "This is absolutely shameful. I had more than a thousand questions on tax credits." He cites one from Paul, who says they need the money to survive. Cameron says we need a country "where work genuinely pays".
12:06 - Cameron reels off statistics and schemes. Corbyn will need to counter that on detail. He thanks him for the answer and his comments on PMQs. He cites the cuts of 1% to rent levels on councils without considering the challenges authorities face. He brings up a question from Steven from a housing association. That will result in many job losses, he says and threatens worse conditions. "Does the PM not think it's time to reconsider the question of funding of administration of housing?"
12:04 - What does the government intend to do about the chronic lack of affordable housing? Cameron stands up and congratulates Corbyn on his "resounding victory". He adds: "I know we will have many disagreements but where we can work together we will do so. If we can change PMQs no-one would be more delighted than me. I welcome it. Let me answer very directly Marie's question." Ok this is different. This is actually pretty weird.
12:03 - Corbyn stands up and celebrates the democratic explosion which led to his victory. He says he spoke with many people about democracy and "our conduct within this place". He says many said they thought PMQs was too theatrical and they wanted their voice heard in parliament. He says he therefore sent out an email to and asked for questions. He got 40,000 replies. He digs at Cameron and says he's sure he'll welcome this as he suggested the same thing in 2005. He starts on housing.
12:01 - Gordon Henderson reminds the House of the Battle of Britain. He asks the PM to pay tribute to the airmen involved. Think we can see where this is going. "Britain stood alone, the only thing which could stop Hitler," he says. It ends there, mercifully. Corbyn is up.
11:59 - Cameron arrives. Nice tan. He looks uncertain. Whatever the mockery the press throw at Corbyn, Cameron will be wary. He knew where he was with the Bunrhams and Coopers of the world. With Corbyn, anything could happen. OK. The clock has struck 12. Off we go.
11:57 - Corbyn is in the Chamber. George Osborne is peering over at him and smiling menacingly.
11:52 - As for today, Corbyn has promised to be studiously polite in PMQs and, as you may have heard, is crowd-sourcing questions. He also toyed with getting other Labour MPs in to ask David Cameron questions, but seems to have dropped that. Of course, almost all political leaders start promising to reform PMQs - not least Cameron himself. It rarely happens. Corbyn though - he's a different beast. We're in uncharted water.
11:43 - It's hardly Apocalypse Now. But this is the type of thing which gets magnified if you don't speak to the media. A sense of siege warfare develops and small events like this - which plainly was not Corbyn's fault - play into a larger narrative. Basically, the advice is coming from all side: get a press person and do it quickly.
11:42 - And then there's the cameraman thing. It looks like one of them got too close to Corbyn's driver this morning and was shoved to the ground. Here's the video:
11:33 - Well first Corbyn put out a statement on the national anthem business. It was very strong and sensible.
Yesterday the Tories cut tax credits taking money from 3 million people. No mention of that on our media front pages. pic.twitter.com/wMBlg4GZq7— JeremyCorbyn4PM (@JeremyCorbyn4PM) September 16, 2015
But then, bafflingly, a Labour spokesperson said he would be participating "fully" in future events of this sort. That means singing. Quite who this spokesperson is is another matter - Corbyn has no spiners or press people.
Labour sources say @jeremycorbyn will sing national anthem at future events— norman smith (@BBCNormanS) September 16, 2015
So now we're back in the land of God-knows. This is pretty typical of the way things are going so far - initial principled position expressed, then a total failure of communication, and then a retreat. It's not a good pattern. I've argued that Corbyn urgently needs a media strategy here while Adam argued he was right not to sing the anthem here. But whichever way he approached it he needed to stick to it - if it's principle then don't bend. If it's the usual politics game, then don't initially start with a principled position.
11:30 - While I'm tackling the live blog my colleague Adam Bienkov will be in the Chamber for the event and writing a verdict immediately afterwards. In the mean time, let's update on today's events. Corbyn is currently averaging two scandals per day. The two today are on his refusal to sing the national anthem and this stuff about a BBC cameraman being shoved to the ground outside his house. Let's cover them both in turn.
11:16 - Good morning. It's like old times here at Politics.co.uk towers. We used to do these PMQs live blogs all the time. It was an excuse to be dreadful about politicians in real time. But after a while we decided it didn't get the traffic to warrant the amount of manpower it demanded. However, it's now back for one week only - unless we decide for some reason to change our minds again, as we often do. It's back because it's Jeremy Corbyn's first ever PMQs as leader of the Labour party. For once PMQs is utterly unpredictable - you can imagine him killing it or falling apart completely. After years in which it was a grotesque slab of boredom in the working week, it finally feel vital again. Kick off is at noon.