It's not even a funny joke it was a insult in case anyone has forgotten he then followed it up with a suggestion about bank robbers , it's a typical white upper class twit jibe ,which they think they can make out of some deluded thought born from being a toff , were all supposed to say ,oh silly old Boris, or silky old Prince Phillip , there upper class snobs and arrogant with it.
Most of us, although not supportive of the gear they wear as it is suppressing womanhood in its very nature, and I'm guessing a lot would not be allowed out if not worn, would never utter these Boris type views , his privalge allows him to get away with it ,in this age of disliking foreigners.