I love how he's the only one that looks uncomfortable, really adds to the surrealness of the scene.
He'd love to pose for the camera but now he is holding the police helmet he is worrying that the next copper along would assume he was taking the piss and clobber him. It's a complex mask of conflicting impulses.
As an American I don't understand what's happening here. They are clearly some kind of police force but I don't see any military hardware, there's no blood, there's no guns anywhere, and the people near the police are still not beaten up and arrested.
Those must be the most stoic brave superheros that manage to survive despite all the danger!
:P
We've got loads of culture, it's just that the rest of the world has appropriated it and no longer recognises it as ours.
E.g. the suit. George Bryan "Beau" Brummell is responsible for that (he died 'shabby and insane' in France, perfectly British). It could easily have gone a different way and we'd all be wearing lederhosen to work, weddings, and funerals, but there you go.