Is Theresa May's shock election call a risk worth taking?

Theresa May: Is her gamble justified?: PA

Two years ago, the general election was meant to usher in the peace of a majority Government after the civil wars of Coalition.

Then last year’s referendum was supposed to settle the European question for a generation.

So today’s announcement of another general election by a Prime Minister who repeatedly promised “stability” can be taken as a wish rather than a guarantee.

With a 21-point Tory lead in one weekend poll and superlative approval ratings, Theresa May is taking a justified gamble that she cannot lose against Jeremy Corbyn, whose personal ratings are shockingly low, even among Labour supporters.

She handled the risk decisively, snuffing out speculation by denying that an early election could happen, thus avoiding the fate of Gordon Brown who agonised openly before bottling it in 2007.

Every poll, every pundit and most independent-minded MPs agree that a big Conservative majority is likely. Investors certainly thought so - for the Pound jumped during Mrs May’s statement.

With a lucky campaign, she might even achieve the biggest landslide since Margaret Thatcher trounced Michael Foot in 1983.

But we live in an age where experts keep getting confounded by real life - from Westminster to Washington.

And Mrs May has an awful lot to lose if things go wrong, including a Tory Party that is remarkably united under her leadership at the moment.

The immediate pressure is on her opponents. Mrs May hopes to bite into Labour heartlands in the North West and North East where voters turned overwhelmingly Brexit last June.

If she succeeds, it would be not just a blow to Mr Corbyn’s survival hopes, but to Labour’s long term health.

In Scotland she hopes the pendulum will swing away from Nicola Sturgeon, weakening the SNP’s campaign for a second independence referendum within two years.

The stakes are high for the First Minister, whose lifetime aim of ending the Union could hang on maintaining her unprecedented 2015 gains.

London is a perfect microcosm of the shifting political sands where an unwary step will see party leaders swallowed up.

Labour did well in the capital in 2015, outperforming other regions. But if the recent YouGov poll of Londoners, which put the Conservatives just three points behind Labour in the capital, is right then those hard-won Labour gains masterminded by Sadiq Khan before he left to become Mayor will be battlegrounds again.

A clutch of North London Tory marginals, like Bob Blackman’s Harrow East, would turn a deeper shade of blue if YouGov was right. It might even mean the Tories winning back lost marginals like Enfield North.

But what of the Tory gains that help offset their losses in 2015, such as Kingston & Surbiton and Twickenham?

Those recently knighted former Liberal Democrat Cabinet ministers, Ed Davey and Vince Cable, are on the comeback trail, hoping to splash yellow paint over South West London.

Sarah Olney’s successful anti-Brexit by-election campaign suggests they have a chance.

Remoaners might even have the same impact in this election that Ukip had in 2015 - not winning seats but tilting the outcome in a handful of finely-balanced marginals.

Will Ukip voters be as loyal to Paul Nuttall as they were to Nigel Farage? Will they turn out at all, now that Brexit is happening?

The answer to that could determine the fate of MPs like Minister for London Gavin Barwell, who clung on by his fingertips in Croydon Central last time.