Labour's manifesto, unanimously approved at the party's traditional Clause V meeting, is the most radical programme put forward by the party for a generation. The document includes pledges to renationalise the railways, Royal Mail and the energy grid, build 100,000 new council homes a year, abolish tuition fees, invest £250bn in infrastructure, spend £6bn a year more on the NHS, £1.6bn a year more on social care, raise the minimum wage to £10 and restore collective bargaining.

Jeremy Corbyn's team believe that a "transformational" offer is their best hope of drawing attention away from Brexit (an issue on which the Conservatives poll best) and motivating turnout. With the exception of Trident renewal, Corbyn has put forward a programme that is true to his lifelong principles and to the platform on which he was elected in 2015.

But it's not only the Labour leader who craved a radical manifesto. After winning the Trident feud, most of his internal opponents have been content to let him have his way. This is partly because they agree with many of his popular policies, welcoming the doorstep reception for a higher minimum wage, more NHS spending and free school meals. But it's also because Corbyn's opponents are determined that he "owns the result".

The phrase dates from the 1983 election, when Labour's "old right" gave the left a free hand over the manifesto in the hope they would be blamed for the ensuing defeat (read John Golding's Hammer of the Left for a full account). The party subsequently elected Neil Kinnock as leader, who abandoned stances such as unilateral nuclear disarmament, mass nationalisation and EEC withdrawal.

Since Corbyn's re-election in 2016, most Labour rebels have avoided public criticism of their leader, a stance they have maintained since the election was called. With defeat regarded as inevitable (winning 185-200 seats is viewed as "a good result"), they aim to discredit Corbyn and the left by declaring the electorate has rejected their programme. Never before has Labour's Campaign Group been tested in this manner.

Former MP Michael Dugher recently told me: "The left have always been in the fortunate position of being able to blame the moderates, the centre for when we’ve lost. But whenever we’ve won, they’ve banked it, saying anyone would have won. 'Jeremy Corbyn could have in 1997' - not sure that’s the case, actually. For the first time, they are going to be put to an electoral test themselves: they’ve got the leadership, it’s Jeremy’s shadow cabinet, it will be his manifesto, the public are fairly clear about what Jeremy believes in and the direction of the party, so let’s see how it does electorally."

Some Conservatives, meanwhile, fear that Labour is dragging them to the left by making hitherto "radical" policies (such as an energy price cap and workers on boards) appear acceptable. But others relish a manifesto that they believe condemns the party to defeat.

Labour's poor local election results offered a preview of some of the excuses that will be offered if the opposition does lose: media hostility, party disunity and Ukip's collapse. But don't be surprised if some previously loyal Corbyn supporters lay the blame at his door. For the left's future prospects, it may suit them to argue that the problem was not the message but the messenger.