This whole bit is made all the funnier by knowing that all of the guards were just random extras who weren’t told what was going to happen only that they weren’t allowed laugh at any cost as they wouldn’t be payed if they did.
Um, that’s Chris Langham. Who was certainly not an “unknown extra” even then. He’d already written for Spike Milligan, the Muppet Show, and Not the Nine O’Clock News (both of which he’d appeared on as well).
He was also in The Thick of It, until, well, there’s triggering bits of what happened next.
But even when I first saw Life of Brian (it was unbanned in Ireland when I was 14/15 - my sister took me to see it even though I was below the age of the certification and we loved it), I recognised Chris Langham as that bloke who’d been in absolutely everything.