Britain will once again be going to the polls in June, after Theresa May surprised everyone by calling for a snap general election. The Fixed-terms Parliament Act, it seems, is a mere formality.

The Prime Minister has explicitly framed the forthcoming election as a choice between her Government’s vision for Brexit, hazy though that remains, and those who would “jeopardise” a successful withdrawal from the European Union. It is a referendum by any other name, albeit one using a mechanism – constituency-based elections – that is distinctly unsuited to the task. Indeed, to call a general election over a single issue such as this exposes the naked cynicism behind Ms May’s announcement.

On numerous occasions, the Prime Minister has said in clear terms that she would not call an election until 2020. A walking holiday in Wales appears to have changed her mind, convincing her that only an election can provide the “strong and stable leadership” required to see the country through and beyond Brexit.

But this is only the half of it. Behind the decision lies a calculation (buoyed by recent opinion polls) that Labour will fare worse under Jeremy Corbyn now than they might under another leader in three years’ time; and that it is better to take the plunge now, when talk of a “progressive alliance” among opposition parties is no more than idle chit-chat.

What Theresa May said and what she really meant, according to John Rentoul

Likewise, while the Prime Minister argues that she will be better placed to negotiate a successful Brexit if she has a clear parliamentary majority at home, the reality is that she must believe there is a greater chance of selling the promise of a good deal to the British public this summer than the details of the final withdrawal contract in due course. It is a deeply cynical ploy which, contrary to Ms May’s claims, puts party politics above the national interest.

For Labour, the next 50 days will be an uphill struggle. Corbyn must first unite his own party and then convince the electorate that he has both a vision for Brexit and a broader policy agenda that will bring benefits across the board. His supporters will hope he can tap into the anti-establishment wave ridden so successfully by Donald Trump, without making an explicit comparison between the two men. Labour’s best chance may be to pick up votes lost to Ukip in 2015, but there is no reason to think that is a given.

The Liberal Democrats are the opposition party most likely to benefit from an early election, in part because of its clear and well-established position on Brexit but also because its base in Parliament was so badly eroded last time round. The party has picked up council seats regularly since the disaster of 2015 and a strong showing in the local elections due to take place in May would put more wind in Lib Dem sails. The SNP, dominant in Scotland, will also be confident in its chances, and as keen as the Prime Minister to present the election as a stark choice: not only on Brexit but, as ever, on the future of the UK. It remains to be seen whether that will work in the SNP’s favour.

In the end, there are two obvious paradoxes at the heart of Ms May’s position. First, she decries what she sees as “political game-playing” by the opposition at Westminster, and yet plays politics herself by presenting the election as a “my way or the highway” style run-off.

Second, she rages against the lack of unity at Westminster, arguing that any opposition to the Government is the cause of instability. Yet surely it is the primacy of Britain’s parliamentary system which those who voted in favour of Brexit were seeking to protect. And parliamentary democracy works not in spite of effective opposition to government plans but because of it.