Wednesday 25 May 2016 6:30 am

RMT’s vote for a strike over Night Tube will be Sadiq Khan’s first test as mayor of London

Well, that parade has been been well and truly rained upon. At the start of this week, TfL announced – to widespread cheers – that the long-promised Night Tube would (finally) launch in August. That promise remains on track, but yesterday the sense of triumph was darkened by the prospect of more strikes.

The RMT, which has been the most belligerent of unions during Night Tube negotiations, said a ballot of maintenance and engineering staff working for Tube Lines, a subsidiary of TfL, had voted in favour of a strike thanks to “major unresolved issues” over pensions and performance-related pay.

Thus, following months of painstaking negotiations, it seems as if the saga has not yet run its course. The Night Tube, let us not forget, was originally supposed to launch last summer.

The good news is this: Tube Lines workers don’t cover the Victoria and Central Lines, which will be the first 24-hour lines to launch in August, so there will be no delay to the service’s initial launch.

But strikes by maintenance workers have caused chaos in the past. Which means this dispute is likely to become the first major hurdle for Sadiq Khan as mayor of London.

Khan famously criticised Boris Johnson for not attending negotiations with unions, and in February even went as far as to insist there would be “zero strikes” if he won the mayoral election, against Boris Johnson’s 35 days.

At the same time he also said he will “make sure that I’m talking to everyone who runs public transport” to ensure negotiations over pay and conditions run smoothly.

So far, so soft.

Now he is in office, Khan may live to regret his words. If Johnson’s team learned one thing, it is that niceties are quickly dispensed with in disputes like this. Unions want one thing, a solution to their members’ gripes over pensions and hours, no matter what their previous relationship with the person on the other side of the table.

Khan faces a stark choice – going soft on the unions, or maintaining his predecessor’s tough stance.