An initial sign of the success of the Corbynista group, Momentum, is likely to come from the deselection of moderate Labour councillors rather than of Labour MPs; having first removed the former, it will be easier to ditch the latter. Getting started on the councillors also reflects the constraints of the electoral timetable.

Mark Wallace has written about what is happening in his borough of Lambeth. His piece has gained national attention and has made it much harder to deny that Momentum are a mechanism for far-left entryism into the Labour Party. It is a repeat of what we saw 30 years ago. It is not confined to Lambeth. I have reported on what they are up to in my borough of Hammersmith and Fulham.

In Birmingham, Cllr Majid Mahmood, a staunch supporter of Corbyn, has managed to secure the deselection of Cllr Anita Ward – a former Lord Mayor and Chairman of the British Legion in the city. They are both councillors for Hodge Hill. I wonder how many new recruits there have been to the Hodge Hill Labour Party, courtesy of Momentum, in recent months?

It’s early days. The scale of the challenge for Momentum is considerable. I’m not aware of a single Corbynista council at present – certainly not Islington. But the temptation will be for other Labour councillors to appease them.

For instance, Cllr John Clancy, the new Leader of Birmingham City Council, is not a Corbynista. But he relied on Corbynista votes to get his new job. Not only Cllr Mahmood – but also Cllr Nawaz Ali and Cllr Habibur Rehman. The more Corbynistas there are in the Birmingham Council Labour Group, the stronger Cllr Clancy’s position is – for the time being.

So will there be a return to the 1980s with the “loony left” running several of our town halls? In some ways it will be different. At that time Labour councils adopted their own foreign policies. New rules prevent, for example, using Pension Funds to boycott Israel – something Jeremy Corbyn has demanded.

Cllr Kieran Quinn, the Labour leader of Tameside and chairman of the Greater Manchester Pension Fund, is indignant, telling the FT, that the government is “trying to restrict funds’ ability to disinvest”.

Then there is the question of a Labour council refusing to cut spending. Even before Corbyn’s leadership, this demand would crop up – for instance via the Unite Councillors Network. The choice would be for them to hold a referendum asking for a big Council Tax increase – or to simply refuse to set a budget, resulting in officials from Whitehall coming in to run the Council for them.

But even with the constraints of the realities of power, Corbynista councillors could still inflict real harm and division on their communities. Thus far, moderate Labour councillors have been fairly craven about the threat they face. They have a duty to speak out – and to fight back.