Image caption The four 1970s prime ministers changed the nature of the clashes

It was on this day 50 years ago that Conservative Prime Minister Harold Macmillan and Labour leader Hugh Gaitskell squared up for the first official session of Prime Minister's Questions, following an initial experiment earlier in the year.

They are the highlight of the parliamentary week, with a packed Commons chamber and public gallery, and a television audience around the world.

But PMQs, as they are known at Westminster, have changed radically along the way.

The 1970s was the key decade in their development. It saw the clashes of Jim Callaghan and Margaret Thatcher and the first radio broadcasts of the session as well as the bitter duels between Harold Wilson and Ted Heath.

Image caption Harold Macmillan was the first minister to take part in the original twice weekly question time

The speaker in the early 70s, Selwyn Lloyd, said he thought the personal animosity between Heath and Wilson had poisoned PMQs.

But Ted Heath said: "I think in politics it's not a question of going out and liking people or not, it's a question of dealing with people."

Harold Wilson's senior policy adviser Bernard Donoughue said he "didn't sense that Harold Wilson positively disliked Heath" but identified them as being very different characters.

"Each was uncomfortable with the other. Harold just felt that Heath was a rigid, stiff, intolerant judgmental person… and I think Heath had contempt for Harold, because he felt Harold had no deep principles," he said.

Find out more Dominic Sandbrook presented Archive on 4: Mind Your PMQs on BBC Radio 4 at 20:00 BST on Saturday 22 October Catch up on iPlayer

"Normally Harold Wilson came out on top as he was more suited to that kind of verbal, mental game.

"My observation and understanding is that all PMs are very nervous (before PMQs). Wilson was very nervous and would open the brandy bottle beforehand, and certainly open the brandy bottle afterwards, as it's the most testing time for a PM.

"It's when Heath was really on show, and if he got questions wrong, it was seriously held against him in the Westminster village.

"They were so different in their character, there was no mutual respect, no empathy between them."

Sparring partners Prime Ministers listed first: 1961: Harold Macmillan v Hugh Gaitskell 1963: Alec Douglas-Home v Harold Wilson 1964: Harold Wilson v Alec Douglas-Home 1965: Harold Wilson v Edward Heath 1970: Edward Heath v Harold Wilson 1974: Harold Wilson v Edward Heath 1975: Harold Wilson v Margaret Thatcher 1976: James Callaghan v Margaret Thatcher 1979: Margaret Thatcher v Michael Foot 1983: Margaret Thatcher v Neil Kinnock 1990: John Major v Neil Kinnock 1992: John Major v John Smith 1994: John Major v Margaret Beckett 1994: John Major v Tony Blair 1997: Tony Blair v William Hague 2001: Tony Blair v Iain Duncan Smith 2003: Tony Blair v Michael Howard 2005: Tony Blair v David Cameron 2007: Gordon Brown v David Cameron 2010: David Cameron v Harriet Harman 2010: David Cameron v Ed Miliband

Until the summer of 1975, most people had never heard PMQs. But that June, the BBC and Parliament agreed to a month-long trial, broadcasting the sessions on BBC Radio 4.

It was only in 1978 that the Commons allowed the BBC to broadcast live.

For many MPs, including Harold Wilson, it was a deeply controversial move. They thought it would reduce the great debating chamber to a beauty contest.

At the time, the Conservative party leader was Margaret Thatcher. Her adversary was Labour prime minister James Callaghan, who easily brushed her questions aside.

Michael Dobbs, who worked for Margaret Thatcher while she was in opposition, said while Callaghan was tough to beat, Thatcher got a hard time simply for being a woman.

He said: "Not only was she patronised, at times by 'Sunny Jim', who with his wonderful manner was able to pat her on the head, and suggest she sit down and calm down, but much more vigorously and violently by the reaction of the Labour backbenchers.

"In those early days, when she was nervous and her voice reached a certain height - they would screech at her, and they would mock her.

"It was incredibly patronising and sexist, but they did it in droves. That was their weekly fodder, to knock her off her stride, and there were many occasions in those early days when Jim would come away with a victory."

"She used to care about those setbacks passionately... to lose out on one occasion used to really upset her, but the way she dealt with that upset was to go back and do it better."

Mr Dobbs said Thatcher used to prepare and over-prepare, and continued to do so after she won the 1979 election.

Image caption Margaret Thatcher got through more PMQs than anyone else because of her many years in power

And Thatcher changed PMQs. Previously prime ministers had been happy to transfer questions to other ministers - but she fielded them all, including supplementary questions, herself.

PMQs used to be held in two 15-minute slots on Tuesday and Thursdays, but when Tony Blair became prime minister, he replaced both with a single 30-minute session at midday on Wednesdays.

MPs have over time mastered the art of asking the "right" question said Dr Mark Sheppard, who has studied PMQs. "MPs have realised that if you're going to ask a question, it's going to be on a hot issue of the day, and you might as well frame that or connect it to your constituents."

"In the early 70s, one in five Prime Minister's Questions would have very personalised constituency questions.

"If you look at it today, then all Prime Minister's questions have personalised constituency questions.

"You want to make sure you are going to communicate with your constituents, as after all they are the ones who are going to re-elect you."

The level of rowdiness at Prime Minister's Questions sometimes is excessive and it is damaging John Bercow, Speaker

While some would argue it has become an exercise in one-liners and one-upmanship, others feel the house has become too rowdy.

The current speaker John Bercow said there was still work to be done to improve it further.

"It has become a less congenial and less collegiate occasion that once it was, and as long ago as the mid-1990s the procedure committee looked at and proposed a series of possible reforms to improve the situation but none of those was taken up," he said.

"Critics feel that it has become an occasion for grandstanding on either side of the house, for perhaps questions that aren't always questions and answers that aren't always answers.

"There has been over the generations a decline of deference and an accentuation of aggression and negativity and pejorative criticism of each other in politics, and secondly I think there is always the desire of the party to be able to say we won the boxing match.

"I don't think we should make out that it is worse than it has ever been. I do think that the level of rowdiness at Prime Minister's Questions sometimes is excessive and it is damaging.

"Prime Minister's Questions is the shop window of the House of Commons.

"It is, by a huge margin, the most viewed event of the parliamentary week. And all of that, together with all over the other work Parliament as an institution does, can ultimately count for very little if that half-an-hour session degenerates in to extreme commotion, disrespect, turbulence and uproar and the public take a dim view of it."

Archive on 4: Mind Your PMQs was broadcast on Saturday 22 October at 20:00 BST and is available on the BBC iPlayer.