It’s all played out like inconsequential fluff – certainly everyone acts like the oncoming danger is all a bit of a lark, rather than actually terrifying – but it’s as smart, clever and sexy as you’d expect from showrunner Steven Moffat in a TARDIS-bound story that lasts less than ten minutes. Indeed, there’s every reason to think that a couple of moments in this tiny segment may well lead in to Series 6 (just what is Amy needing to speak to the Doctor about at the start?).

Since there’s only a couple of minutes to play with, any quotes (no matter how minor) would constitute a major spoiler. Suffice to say, the fate of the TARDIS crew rests entirely on a glimpse of Amy Pond’s legs – no, really. The fact that this Red Nose Day special gets a review all of its own is indicative that this is a proper canon adventure – played slightly more for laughs, sure, but still a proper story, and for all that, it’s near perfect.

Given that this was created for Comic Relief, it seems somewhat churlish to award stars: it’s certainly as funny as ‘Curse Of The Fatal Death’, not as touching as ‘Time Crash’, but easily better than ‘Dimensions In Time’ – and well worth you nipping over to rednoseday.com/donate.

Airs on Friday 18th March 2011 on BBC One.