It became apparent that Muhammed Butt, leader of Brent Council, had become a national member of Momentum. It must have been rather disconcerting to have 'The Leader' in the meeting, particularly when he is thought to support the nomination of his fellow Cabinet member Cllr Krupesh Hirani.
Cllr Butt is not well known for his red-blooded socialism, militancy over academisation or refusal to implement cuts. Hitherto, he has been more pro-Sadiq than Jeremy, so people were rather stunned by his apparent conversion to the cause.
As if to confirm his new status and silence the doubters, Butt turned up at the Momentum protest outside the Willesden Green branch of Barclays Bank on Saturday, part of a very worthwhile nationwide campaign by Momentum against the bank investing in fossil fuels and thus contributing to climate change. His presence attracted many tweets and re-tweets.
So has he been converted to the cause by Graham Durham and co, or is there more to it? When his party commanded 57 of the 63 seats on the Council he was successful in seducing the three Tory councillors from Kenton into what amounted to an alliance against the Brondesbury Park conservatives.
Perhaps Butt's move is a sort of reverse entryism: Uncle Mo keeping a wary eye on the combination of Old Campaigners and Young Turks.