The Socialist Party has backed Gordon Brown for Labour leader! Unbelievable? Can't be true? No, it's true.

Of course the Socialist Party's paper, or its members whom you meet on the street, do not support Brown. Indeed, they will tell you that all the goings-on in the Labour Party are an irrelevance, and they didn't even support John McDonnell's leadership campaign. Anything in the Labour Party is too right-wing for them.

But what do the Socialist Party do where what they say makes a difference? Where they occupy strong positions within the powerful unions affiliated to the Labour Party?

In the TGWU (now part of Unite), the Broad Left, which commands a majority on the union's General Executive, voted to back McDonnell.

The BL members on the Executive never pushed for a nomination for McDonnell; and now that same BL-majority General Executive has nominated Gordon Brown.

There is a lot of disquiet about this in the Broad Left.

But what does the Socialist Party say about it - through Theresa Mackay, chair of the rural, agricultural and allied workers' trade group of the union, an influential figure in the Broad Left, and by far the SP's most prominent member in a big Labour-affiliated union?

At the TGWU London Broad Left meeting on Monday 21st - so we hear from Gerry Downing, a longstanding TGWU activist, who was there - Theresa Mackay responded sagely to the effect that the General Executive had no choice. The union had to nominate Brown if it wanted to keep "in" and get concessions from the Labour leadership.

"What, crumbs?" responded another Broad Left member, Bronwen Handyside. It was close to the end of the meeting, so there was no full debate.

But far from the SP leading the fight against the TGWU leadership's shameful decision to endorse Brown, the SP - where it mattered, where it had people with real influence - was rationalising for it.