Two weeks ago, Jeremy Corbyn used PMQs to ask Theresa May about Amber Rudd’s resignation, the UK’s disappointing economic growth, A&E waiting times, school budget cuts, the link between police numbers and serious violent crime, and council tax rises – six questions, six topics, just under 800 words. Last week, he devoted all six of his questions, and fewer than 500 words in total, to the Conservative Party’s splits over Brexit.

Tight, pointed questions on a single topic that’s difficult for the government are nearly always tougher for the Prime Minister to handle than unfocused rambles from one issue to another. So it’s no coincidence that last week’s PMQs was a comprehensive victory for Jeremy Corbyn, while the previous week’s, where the leaders’ exchanges took a full four minutes longer, was a dull and inconclusive mess in which the Prime Minister – despite the loss of her Home Secretary a few days earlier – was not seriously troubled.

For the team that helps the Leader of the Opposition prepare for PMQs – a team I was part of between 2010 and 2016, working for much of that time alongside Ayesha Hazarika, co-author with me of a new book, Punch & Judy Politics: An Insiders’ Guide to Prime Minister’s Questions – choosing the topic is one of the most important tasks. It’s not always as straightforward as it sounds. Nor is writing the questions. Lord Bruce Grocott, probably the longest-serving PMQs prep veteran of all, who worked on it with successive Labour leaders starting with Neil Kinnock in the mid-1980s and finishing with Harriet Harman’s second spell in 2015, always used to say that he knew we were going to have a good week if Ed Miliband’s questions could fit on a single side of A4 paper. Too often, they couldn’t. Last week, but not the week before, Jeremy Corbyn’s probably could.

When we asked Ed Miliband to reflect, in an interview for our book, on choosing the topic for PMQs he said that there is “a kind of tug-of-war between the strategic imperative and the strategic case you’re wanting to prosecute, and the day-to-day, week-to-week policy issues that arise”. William Hague told us something similar: “You’ve got the choice of the subject, and that means you’ve got to be more reactive to the news agenda, how the media will regard it, and you’ve got to balance what is a really good line of attack, or what’s an important line of attack, and they may not be the same thing.”

That balance is not straightforward. If you ask about the issue that’s leading today’s front pages and news bulletins, you’ve got a good chance of getting a clip onto the evening news, and your message in front of a wider audience than the small number of people who are watching live. If you ask about something you care deeply about, but where the media has yet to take an interest, you might win a victory on the day but find that nobody else notices. (Too often, Jeremy Corbyn has asked about issues that are unlikely to win him any media coverage, and then failed to win anyway).

If you ask about the most obvious topic, but a weakness in your own position means that you get beaten, you’re worse off than if you’d asked about something else. But if you spot the weakness beforehand and ask about something else to avoid being beaten, you might well end up highlighting that weakness anyway, as people work out why you ducked the story of the day.

PMQs is a joust, not a seminar, and if you’re in it you have to try to win. Choosing to fight on weak ground is asking for trouble. One of the most important uses of PMQs is in forcing each side to identify internally what its weaknesses are, and to take action to put them right.

If the opposition is divided, the Prime Minister will pick up on it – which may be one reason why Jeremy Corbyn has so rarely asked Theresa May about Brexit, even though it has dominated politics for the last two years. Beating any Prime Minister at PMQs on one of the government’s areas of strength is hard – which may be why in the run-up to the 2010 election David Cameron, despite trying to position the Tories as a party that could be trusted on public services, hardly ever challenged Gordon Brown on the NHS.

And whenever an opposition politician has said something unhelpful, the Prime Minister can be expected to quote it at PMQs – which is why on Ed Miliband’s team we spent time pulling together a weekly dossier of the most damaging stories, which we privately referred to as the ‘bucket of shit’, for use in PMQs prep. We used this on Wednesday mornings in run-throughs, in which I would play David Cameron and throw abuse at my boss, trying to anticipate both the Prime Minister’s policy answers and his political attacks with varying degrees of success. Quite often, the run-through would force a redrafting of the questions, or even the abandonment of an entire topic.

One of the few advantages the opposition has at PMQs is the element of surprise. But leaders of the opposition are not always surprising. Margaret Thatcher found Neil Kinnock quite predictable. Alastair Campbell told us that he could only recall one occasion in his time working in Downing Street when Tony Blair’s team did not correctly guess the Leader of the Opposition’s choice of topic. One of Theresa May’s advisers told us that her team has a very high success rate in predicting Jeremy Corbyn’s main subject at PMQs, and that “usually there’s a discussion that takes place for thirty seconds in which we say, ‘Well, he could ask about Brexit’, and then someone reminds us that he won’t ask about Brexit”.

For a long time, that has looked like a safe assumption. But last week, Jeremy Corbyn’s Brexit questions made that Downing Street discussion more difficult for the foreseeable future. That, in itself, is a small victory.

Tom Hamilton was the Labour Party’s Head of Research and then Head of Briefing between 2010 and 2016, and was part of the team that helped to prepare Ed Miliband, Harriet Harman and Jeremy Corbyn for PMQs. 

He is the co-author, with Ayesha Hazarika, of Punch & Judy Politics: An Insiders’ Guide to Prime Minister’s Questions, published by Biteback on Thursday 17 May