Crowded cities need certain unwritten rules to keep them functioning. You don’t stop dead in the middle of a pavement without warning. You let people off of the train before you try to get on.

One of the most important in London – one that all Londoners instinctively understand, and get visibly huffy about when tourists, inevitably, don’t – is that, on an escalator, you always stand on the right. The left hand lane is reserved for those who are in a hurry to walk up or down. It’s clear. It’s simple. And it’s helped keep the users of London’s Underground network moving for a century and a half.

Anyway, Transport for London is experimenting with scrapping it.

You can tell quite what a dangerous precedent this is by the fact the Standard capped up the word yes.

Londoners are taking it well, though.

Once we’d recovered from the shock, thanks to a few deep breaths and a quick go on the smelling salts, we started thinking about the practicalities of this one. The Standard report said that the move was “aimed at smoothing the flow of people out of the busy station”.

But how can you make people flow faster by stopping them from moving? Surely if you make everyone stand still you won’t be smoothing the flow so much as preventing it? What is this madness?

So, we rang TfL and ask them what gives. The answer, it turns out, is that hardly anyone actually is walking up these specific escalators at all, because they’re so bloody long. A spokesman told us:

“We get a lot of congestion at the bottom because the majority of customers don’t want to walk. The left hand side empty, while everyone is queuing up to stand on the right. By filling up both sides, we can actually carry more people more quickly and clear that congestion.”

In other words, the flow it’ll be smoothing isn’t on the escalator at all, because hardly anyone was bothering to climb them: it’s in the queue to get onto the things. By preventing a small number of people from walking up the escalator, TfL hopes to effectively double the standing room on the escalator, and slash the queuing time for everyone.

That said, this is only workable because the escalators at Holborn are quite so long: if people were genuinely walking up the left, it might just slow things down. And even there, there’s a chance it won’t come off. As the spokesman said:

“It’s a short term trial and we’re going to see how customers respond to it.”

In the mean time, if you want to be shouted at by TfL staff with megaphones that you absolutely should be standing on the left, then the trial will be going on for the next three weeks.