So it is a propitious moment to take stock.  It is just four years since Jeremy Corbyn won the leadership of the Labour Party to the astonishment of almost everyone.  Scarcely less remarkable is that he is still leader four years on, despite intransigent and unabated opposition from the Establishment and its powerful supporters within Labour itself.

That Corbynism has endured and, indeed, taken Labour to 40 per cent of the poll in its only general election test to date is surely due to a confluence of factors — the post-2008 crisis of neoliberalism which, inter alia, swept away the political and economic assumptions of New Labour; the development of left-led mass movements against war and austerity which sought a more comprehensive political expression and the deep-rooted and long-frustrated desire of millions of people for that alternative which Thatcher and Blair insisted didn’t exist.