Harold Macmillan in early 1963 - before the carnage began

July 13th 1962: The Night of the Long Knives

July 13th 1962: The Night of the Long Knives

You're watching the Open on the television. And then, from nowhere, the coverage is interrupted. It's a newsflash. A Cabinet reshuffle! Out of the blue, the prime minister has torn the heart out of his government.

Nothing like this had ever happened before. The press mockingly call it the 'night of the long knives', after Adolf Hitler's brutal move against Ernst Rohm's SA. Harold Macmillan's reputation was shattered. Although they didn't realise it, nothing like it would happen again.

It's half a century to the day since Harold Macmillan suddenly and dramatically replaced one-third of his Cabinet. But although 50 years has passed, the political situation of 1962 was eerily similar to the one in 2012. A one-nation Conservative prime minister struggling with a failing economy and awkward Liberal colleagues in government. A politically ill-judged Budget.. The sneaking suspicion that an apparently loyal chancellor is manoeuvring. A reshuffle expected in the autumn. Sound familiar?

By the summer of 1962 the Tories had been in power for 11 years and seemed to be flagging, suffering the ill-effects of economic difficulties through a series of terrible by-election results. In March the rock-solid Tory seat of Orpington, located right next to Macmillan's own seat, turned Liberal as a majority of nearly 15,000 disintegrated. The Liberals emerged with a majority of 8,000 – a staggering swing.

Failing to realise that many fed-up Tory voters were choosing to express their dissatisfaction by backing the Liberals over Labour, Macmillan decided that something had to be done. So Rab Butler, the home secretary, plotted with Tory chairman Iain Macleod to shake up the government. Their target was the chancellor of the exchequer, Selwyn Lloyd.

Lloyd was a Macmillan loyalist, but 'Supermac' had become suspicious that his right-hand man was plotting against him. Lloyd's equivalent of the pasty tax had been the introduction of a tax on sweets and confectionery, which the opposition and press had painted as a raid on children's pocket money. Lloyd, like Gordon Brown, was a non-conformist from outside the south of England whose views on the fundamentals of economic policy differed from Macmillan. By the end of June Macmillan was coming up with his own proposals to fix the economy.

The Tory leader faced a quandary. He couldn't make Lloyd home secretary, as Selwyn had made clear he opposed capital punishment. He couldn't make him lord chancellor either, as he didn't Lloyd had enough gravitas for the role. So he had to be jettisoned completely. Macmillan resolved on some new blood with a reshuffle in the autumn of 1962. The calm, dignified, unflappable prime minister had his plan – and he was sticking to it.

He was, at least, until Butler intervened. The best laid plans can be ruined by an unfortunate leak. At a lunch for journalists on Wednesday June 11th, the home secretary blurted out the reshuffle details. The next morning there they were, under the headline MAC'S MASTER PLAN, in black and white. Macmillan felt he had to act, and fast.

What followed was, by the genteel standards of Westminster politics, brutal. Lloyd was at a Buckingham Palace reception on the evening of July 12th when he was summoned to Downing Street to be sacked. On his return he found himself stuck. He couldn't get home, because the ministerial car he had grown so accustomed to was no longer at his disposal.

The next day, the Friday, it was the turn of the other victims. Macmillan, once started, had to finish. He ended up getting rid of seven Cabinet members– out of a total of 21. One of them, the lord chancellor Lord Kilmuir, complained afterwards that "one's cook would have had more notice". To which Macmillan simply responded that it was easier to get new lord chancellors than it was new cooks.

Among the other politicians exiting the Cabinet were John Maclay and Charles Hill, the last National Liberals in government. It took 48 years before the next liberal politician, one Nick Clegg, returned to power at the national level.

Westminster was flabbergasted by the unsubtle bluntness of the change. In one fell swoop Macmillan had polished off a third of his entire government. There were 59 people involved in the knock-on reshuffle of the 102 junior ministerial posts. Butler's slim chances of becoming party leader were finished by the fallout. But it was Macmillan paid the price with the popularity of his parliamentary party. When Lloyd entered the Commons afterwards he was greeted with uproarious cheers; the prime minister was met with stony silence. Even Anthony Eden, the former prime minister, spoke out by saying Lloyd had been "harshly treated". Macmillan knew he had made a big mistake, and regretted it. Afterwards he claimed the thought of the reshuffle made him want t ovomit.

Macmillan was to last another 18 months in No 10, before taking the opportunity of a health scare to withdraw from power. Since 1962 PMs have sacked more ministers – Margaret Thatcher instantly springs to mind – but even the Iron Lady never managed so many in one go. Nowadays we view reshuffles as much as a sign of weakness as one of strength – as Brown's last-gasp reshuffle in 2009 showed.

The Night of the Long Knives was "an act of carnage" which had come out of the blue. It's helped us to become more accustomed to acts of grim self-interested political butchery; but for those witnessing these events as they happened, they were simply unprecedented. The Liberals' future leader, Jeremy Thorpe, mocked Macmillan by observing: "Greater love hath no man than this, that he lay down his friends for his life."

A lesson many politicians have taken to heart in the half-century that's now passed.