Britain’s two longest-serving prime ministers since the 19th century – Margaret Thatcher (11 years, 208 days) and Tony Blair (10 years, 56 days) – have at least one thing in common. They both decided to work in parliamentary terms of four years (approx) and to seek re-election on each occasion in either May or June.

They won every time – each PM adding two re-election wins to their victories from opposition.  Perhaps they recognised that voters feel happier in Spring and early Summer – and that going ‘early’ around the four-year mark, rather than deep into the fifth year, creates a positive impression of energy and boldness.

In fact, in the past 50 years, there has been only one loss for an incumbent PM going to the country in the fourth year of office – Edward Heath in February 1974 when he asked the people: ‘Who runs the country?’ and the people replied: ‘Not you’. Maybe he should have chosen May or June.

Also in this half-century, there were three elections after less than three years of a parliament – Harold Wilson in 1974 (eight months), Theresa May in 2017 (two years) and Boris Johnson in 2019 (approx 2.5 years) – and all returned the incumbents to office, even May who lost her majority after a terrible campaign.

Now what about the PMs who chose to cling to office like limpets on a rock well into the fifth year of a parliamentary term, as permitted by law?

There were three losses: James Callaghan in 1979, John Major in 1997 and Gordon Brown in 2010. A surprise win was John Major in 1992, scoring a personal triumph with his soapbox. Another win was David Cameron in 2015, who unexpectedly defeated both Labour and his LibDem coalition partners, perhaps helped by the Fixed Term Parliament Act (FTPA), which removed speculation about the election date.

So, that’s three losses and two wins for the fifth-year limpets – compared with seven wins and one loss for the ‘four-years-or-less’ PMs. It’s not difficult to work out which strategy is preferable.

Which brings us to Rishi Sunak.

Why on earth hasn’t he called an election in April/May/June this year? Of the 10 elections held in April/May/June over the last 50 years, seven have been successful for the incumbent. He obviously thinks an improving economy will help him later this year but the omens are not good.

If he had been really brave, Rishi could have called an election in Spring 2023, the fourth year of this parliament. His personal ratings were good before stepping up to rescue his party from the rubble of Liz Truss’s 45 days, but they started falling soon after and are terrible now. The Tory party’s ratings have also declined to record low levels. So he probably would have lost in 2023 but perhaps not by as much as he is likely to now.

The lesson for future PMs is: don’t be a limpet – and learn from the two most politically successful leaders of our age that four years is enough and April/May/June is best. Above all, be bold. And, if you want to be a true statesperson, think about introducing another FTPA – but make it four years this time, in line with parliamentary practice in many other countries.

Ladbrokes are currently quoting 1/2 for the Tories losing 201 or more seats, 6/1 for 101-150 seats lost and 20/1 for 51-100 seats lost. There may be value in the last two bets, as funny things can happen with first-past-the-post, but the odds are long for a very good reason.

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