This clip features David Mitchell and Robert Webb in classic form, playing a regular British police constable and a Police Community Support Officer walking down a suburban street. Right off the bat at 00:01, Mitchell's character berates Webb with venomous contempt, calling his PCSO uniform a crappy little community support costume. When Webb tries to defend himself at 00:17 with a mild flipping, Mitchell immediately pulls rank, warning him that swearing at a real police officer is not a good idea.
The absurd tension escalates when a young boy rides his bicycle on the pavement at 00:26. Webb gently intervenes to stop the kid, only for Mitchell to step in and accuse him of community support brutality. To demonstrate what real police brutality looks like, Mitchell casually pulls out his baton at 00:47 and whacks the boy over the head, declaring it something Webb would know nothing about in his capacity as just some guy, before telling the crying kid to be on his way.
It is classic Mitchell and Webb dark satire, taking a trivial institutional rivalry between full police officers and PCSOs and pushing it to a totally unhinged extreme. The deadpan escalation and Mitchell's terrifyingly smug delivery make the sudden turn at the end hilarious, even as it catches you completely off guard.