When shown a video of Piers Corbyn not wearing a mask on the Tube, Mr Khan told Sky News’ Breakfast programme: “Up until only this morning all we could do is ask him to leave public transport, without the ability to issue fines. Because of the changes from the Government overnight he will now be issued with a fine if he did that today.”

He added: “The really important thing is this, we know this rule change, with the ability to have enforcement, the ability to issue fines does lead to behaviour change… before July 19 roughly speaking 85 per cent of those using public transport wore a face mask. We issued almost 2,000 fines before July 19.

Transport for London previously made it a condition of use to wear a mask unless exempt, however this has not been regularly enforced since the lifting of the legal requirement on 19 July.