‘Waking up the morning after the Momentum national committee,” wrote a young woman called Laura Catriona Murray three days ago, “I had that feeling you have after a horrible break-up from someone you love.”

The grieving Ms Murray was writing a blog post about a meeting on Sunday in Birmingham. Momentum is the grassroots organisation that claims 17,000 members and 100,000 supporters and is supposed by some to have been instrumental both in boosting Labour Party membership and in the re-election of Jeremy Corbyn as leader. The shiny enthusiasm of some of its young adherents at the party conference in the autumn had even a few seasoned centrists I know letting slip a nostalgic tear of sentimental identification, like parents at their first nativity play.