Yesterday's Evening Standard has the latest figures on just how many trade union members are signing up to join the Labour party. The figures are terrifying for Labour: but not for the reasons that you might think.

Under Labour's old system, affliated trade unionists were automatically enrolled and voted in the affliates section of the electoral college, which made up a third of the vote. Now, trade unionists must decide to opt-in, and their vote counts for exactly the same as an MP's or a party member.

Theoretically, this handed more power to the trade unions than they'd ever had before. In the last leadership election, the votes of 258 MPs counted for a third of the vote - while the votes of close to 200,000 trade unionists also counted for a third of the vote. If even half of those members had signed up, the trade unions really would have "picked the Labour leader", not just now but in perpetuity.

But since the leadership contest began, just 1,197 trade union affliates have been signed up to vote in London. That's not a typo: barely a thousand trade unionists have joined the Labour party in London since the leadership election has begun. To put that into perspective, Unite, Britain's largest trade union, has 200,000 members in London alone. That's under one per cent.

The trade union movement is not going to be particularly influential in either the Labour leadership or the mayoral selection.

Now, if you are a particularly one-eyed supporter of the leadership campaigns of Yvette Cooper and Liz Kendall, the deputy campaign of Caroline Flint, or the mayoral campaigns of Tessa Jowell, David Lammy and Diane Abbott, that might sound like good news. Think again.

Both Andy Burnham and Tom Watson, who will likely recieve the backing of the majority of the trades unions, are popular with Labour activists and it's near certain that at least one of them will triumph. Sadiq Khan, the union candidate in the mayoral race, however, will likely struggle to beat Tessa Jowell as things stand. But regardless of who wins, the result will confirm the impotence of the affliated trade unions under the new system.

And it would be neither unlikely or unreasonable at that point if at least one trade union were to walk away. Where will a Labour party that looks very far from government get its money then?