"The Leader of the Opposition is the only MP who is allowed to come back with further questions": not so; the leader of the second largest party (currently the SNP, and previously the Lib Dems) gets 2 questions. For example: goo.gl/6S0988

Here's a bit more detail of a Closed Question: thoughtundermined.com/2015/01/29/closed-questions-and-pmqs . Closed Questions are the norm for questions to other departments.

@Steve that may be the case but its not written on the UK Parliament website. If you find me a source I will edit and accredit you :-)

Fair enough :-) Here's some (hopefully reputable) sites which mention this: BBC, politics.co.uk, BBC again, Wikipedia‌​.

Incidentally, William Hague - when interviewed about his time as Leader of the Opposition opposite Tony Blair - developed a cunning strategy to keep the PM on his toes, despite the PM coming prepared with a big folder of possible subjects in alphabetical order: "I invented a new technique of asking questions, which was to only reveal in the final word of the only sentence in the question what the subject of the question was so that he couldn’t find his place in the alphabetical book."

Say that again...haha. I get the intent but not the method of delivery. Hague would ask a question and only the final word of his sentence would reveal the crux so Blair could not find the relevant index letter in his book in time? Can you find any examples? That's brilliant.

politicshome.com/news/uk/social-affairs/politics/…

Let us continue this discussion in chat.

@Chux - interesting point. :-)

I'm assuming "leader of the second largest party" should either be "third largest party" or "second largest opposition party" since the leader of the second largest party is of course, the leader of the opposition?

So Parliamentary procedure requires the first question to be an Open one before a Supplementary one on any topic can be asked? The difference between the need for a written order of questions and the desire to keep questions to the PM secret beforehand makes sense. I guess the presence of Open Questions is the traditional part; MPs and the PM are just playing by the rules?

No. It doesnt have to be Open. I covered that in the answer. You could ask the PM anything and let them prepare a response.

David Cameron deviated from the standard answer in his last PMQs

I'm sure many people have thought of it and there's a good reason it can't happen, but: This is silly. They should update the rules.

@immibis - what? What do you think needs updating and why?

@Venture2099 Well, if everyone is going to use this trick, then there's not much point in the Open Question, is there? They might as well remove it and only have the Supplementary Questions and save everyone's time. (Note I'm not familiar at all with UK's system of parliament)

Did you read the post? They have done away with the Opening question for everyone except the opening speaker.

@immibis: to add to what Venture2099 just said, here's what it looks like in practice, from yesterday's PMQs (scroll down to "Oral Questions to the Prime Minister"). Compare that to the earlier list of closed questions to the Minister for the Cabinet Office.

@Tim: indeed; PMs tend to use the standard answer because it's usually true; but if it isn't, then they don't!

@Necreaux: yes, you're right; and it was more complicated during the 2010-15 coalition, as the 3rd largest party (Lib Dems) were part of the government, so it fell to the remaining small parties to share the extra questions (Wikipedia states that the DUP was allocated one, and one question was shared by the other parties.)