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Blairite, a Brownite, a Corbynite and a Starmerite walk into a Manchester bar. “What are you having, Andy?” the barman asks.

There’s a fine record of Parris declaring that an individual will never make it to No 10, followed by that individual’s promptly doing so: a record Boris Johnson and Liz Truss are both entitled to chuckle at. So you may cheerfully disregard my dismissing Andy Burnham’s chances now. But I do.

More reliably, I think, an online reader comments (beneath a news item about Burnham’s conjectured ambitions) that the Peter Principle is likely to apply. This principle, enunciated in a book of the same name by Dr Laurence J Peter and Raymond Hull more than half a century ago, is that people “tend to be promoted to their level of incompetence”. People keep rising until finally they reach a level for which they are manifestly ill-equipped.

• Andy Burnham attacks ‘divisive’ Keir Starmer before Labour conference