David Cameron’s choice of the word “purred” said it all: a Bullingdon Club posh boy at his most patronising, boasting about his conversation with the Queen.

The Prime Minister should have needed no reminding of the danger of loose talk in the vicinity of radio and television microphones.

John Major’s condemnation of the “bastards”, like Gordon Brown’s tirade against that “bigoted woman”, at least had the merit of being expressions of anger and frustration.

Cameron’s gaffe was of an entirely different order: here he was sneakily revealing – and almost taking the credit for – the Queen’s pleasure at the result of the Scottish referendum, a breach of the royal confidentiality that Prime Ministers were respecting long before he was even born.

Ed Miliband could hardly have done any more to damage his battered reputation for fiscal competence than to have admitted he didn’t mention the economy at his last party conference before the election because the content of his speech was delivered “from memory, and some from the top of my head”.

Whereas Miliband’s ineptitude was no real surprise, Cameron’s was yet another unappealing insight into the way he converses with the gossipy, clubbable clique that he has surrounded himself with in Downing Street.

Cameron should know by now that journalists are on constant gaffe watch for Bullingdon Boy slip-ups, only too eager to exploit stories that play on his upper-class connections. 

His chit chat about the Queen’s response to the No vote in the referendum was something he might have whispered to his wife Samantha or to his closest aides in the privacy of Downing Street but hardly fitting for supposedly off-microphone small talk when being filmed by Sky News.     

Miliband’s initial bravado when talking down the significance of the missing section of his Labour conference speech revealed his misplaced confidence in a willingness to put presentation before content.

Next day he insisted in a string of radio and television interviews that his ability to memorise a 6,000-word speech, and then deliver it from the platform in a conversational style, was what worked best for him and did far more to engage the audience than a prepared script read from an autocue.

In his interview for Channel 4 News, the presenter Jon Snow suggested that the Labour leader’s ploy of delivering a speech without notes was “just a stunt” that played fast and loose with the importance of cutting the deficit which after all was the overriding task facing any incoming government.

Previous Prime Ministers and party leaders have usually been in no doubt about the significance of their conference speech, particularly in the year before a general election when the platform address should be a showcase for party policy and a moment for a carefully-timed personal declaration.

Margaret Thatcher’s aides always regarded her conference speeches as the moment to reinforce her authority within the Conservative Party and later her government.    

At the Tories’ 1980 conference she delivered her infamous soundbite The Lady’s Not For Turning, her strident refusal to change course when faced by a deepening recession and rising unemployment.

Her speechwriter, the playwright Sir Ronald Millar adapted the title of Christopher Fry’s 1948 play, The Lady’s Not For Burning, to supply the Prime Minister with an unforgettable line which was to enter political folklore: “To those waiting with bated breath for that favourite media catchphrase, the U-turn, I have only one thing to say, You turn if you want to. The lady’s not for turning.”

Five of the national newspapers used The Lady’s Not For Turning as the splash headline on their front pages next morning. In later years Millar told me that when he wrote such lines for Mrs Thatcher he always had in his mind their possible use as a soundbite or basis for a headline; he never did better than this in more than a decade of contributing to her speeches.

Ed Miliband’s commitment to increase the number of doctors, nurses and midwives – and to pay for them with a mansion tax and new taxes on hedge funds and tobacco companies – was an equally powerful political statement.

But his speech lacked a well though through punch line that might have made his pledge to safeguard the NHS, and to give its staff the time to care, an unforgettable moment in the 2014 conference season.

Nonetheless Miliband’s aides seemed delighted with his catchphrase “Together” which built on the “Better Together” slogan on the No campaign in the Scottish referendum.

But was mentioning the word “Together” over fifty times in a speech that lasted for more than an hour a sensible substitute for a carefully-crafted soundbite or was it perhaps a tad too trite for the conference designed to rally the Labour faithful for the long haul to a general election less than eight months away in May 2015? 

Illustrations: Daily Mail 25.9.2014; Sun 24.9.2014; Daily Mail 24.9.2014.