What's the art of answering a tricky question?
Prime Minister's Questions is celebrating 50 raucous years. It's long been a stage where masters of the art attempt to answer questions they can't or don't want to answer.
The institution of PMQs has been likened to a bear pit, a gladiatorial contest and an absurd pantomime.
Every Wednesday, sketch writers and political bloggers review the 30-minute bout and score the contenders on their jabbing insults and knock-out sound bites.
In the real world, questions are usually asked with the aim of discovering information. In the theatre of PMQs, many of the people asking the questions aren't angling for facts.
The aim of the game is to score points by discomfiting the prime minister - putting them on the spot in the hope of revealing a gap in their knowledge or forcing an impolitic admission.
Of course, outside politics plenty of ordinary people will have had to cope with taxing questions. For many, the arena of the job interview is where the most gruelling are asked. But could we take any tips from prime ministers present and past?
One important technique the PMs use is to answer the question they wished they had been asked, rather than the one that was asked.
The Independent's sketch writer Simon Carr says three little phrases come in very handy.
"We have always been clear on that…"
"The important point here is…"
"I thought you would have been congratulating us on…"
Ordinary voters may despair of the times politicians don't give a direct answer to a question. Here is the realm of the "non-answer".
"[Politicians] quickly learn how to give a non-answer to a question they either don't want to answer or that they cannot answer," says Chris Moncrieff, the Press Association's former political editor, who has been to most PMQs over the past 50 years.
"Prime ministers are often asked not only about great international events but also about a minor scandal in a local hospital and he is expected to be able to talk about that.
"Very often he will say 'I will be very pleased to meet the honourable gentleman to discuss this matter further'. He hasn't said anything but he has satisfied the questioner."
Moncrieff says the arrival of television in the House of Commons in 1989 encouraged the sound bite, the use of a "sexy, attractive, shocking phrase", usually crafted beforehand on the big issues of the day. It is another great way of answering a question and covering up a mediocre performance.
But he believes the key to answering difficult questions is confidence.
"Always try and sound like the master of what you are saying even if you are doubtful about it. If you make a point, you stick to it through thick and thin - otherwise you're a goner."
This last piece of advice could come straight out of a manual on job interview technique.
Interviewees should try and buy themselves time, says Matthew Riley, an entrepreneur who quizzed this year's Apprentice finalists. Repeating the question back to the interviewer can give you at least 20 seconds to come up with something.
However, his top tip contrasts very strongly with the politician's approach.
"If you don't know the answer, just say," suggests Riley. "I would much prefer people to say 'I don't understand' or 'I have got that wrong, I will look into it'."
A Cameron, Clegg or Miliband might find themselves greeted with laughter should they take that tack.
Prime ministers can never admit a weakness, lack of knowledge - except where the question is local or extremely esoteric - or failure to understand.
Instead they have to prepare, prepare, prepare.
Prime ministers are normally not given any notice of the questions. They can be asked everything and anything, and they are no longer allowed to defer to their ministers.
Their performance is scrutinised as much as their answers.
Political pundit Olly Grender agrees with Moncrieff that Margaret Thatcher and Tony Blair were masters of the despatch box.
The former Liberal Democrat director of communications says Thatcher was given vocal training to improve her performance and Blair would spend "days on end rehearsing".
Grender says many techniques are used to deflect difficult questions - Gordon Brown used to "list 13 things" and the worst example of a reply was when he said he had "only been in the job for five days".
"It is an ability to eke out from the question the thing you want to answer, so if you are offering the question, the tightness of the phrasing is all important."
The prime minister is not obliged to answer every question, Grender says. "If some backbencher asks a facetious question, like 'what's the point of Nick Clegg?'. You just shouldn't answer a question like that."
Carr says backroom staff dedicate hours to working out the opposition's weaknesses. One of Ed Miliband's early techniques was, he says, to concentrate on an obscure bill and, if Cameron didn't know the answer, to accuse him of not knowing his own policies.
"They worked out he was devolving a lot of stuff to his cabinet and wasn't micro-managing, and they hoped to catch him out on the details."
Carr says Blair used his barrister's touch. He says he also had a brilliant "poker face" and his body language oozed confidence.
Blair started getting up quickly to answer a question, and Cameron has followed his lead, he says.
Unlike Cameron, who "sits like he's at church - very respectful, very respecting, slightly commanding", Miliband was always touching his face in the early days.
"Miliband has stopped most of his habits now after he got such a whipping - he would run his long finger over his bottom lip which he would stick over his bottom teeth like a woman applying lipstick.
"Powerful people don't touch their face in public. It makes them look self-absorbed."
When it comes to answering tough questions, it seems confidence is very much part of the act.
An ability to sit still and Oscar-worthy acting skills will also help, as will knowing what you are talking about or at least sounding like you do.