It smells a bit and the door won't close properly but it'll do for the time being. Well, it'll do for this time being!" quips the Doctor as he prepares to head off on yet another time-travelling adventure, this time swapping his trademark blue police box for a far less salubrious portable lavatory.
"The other one broke down next week," he explains, "We're having to have parts specially made back on Gallifrey, but all being well they should be ready sometime in 1968. Can't wait to be honest."
He goes on to explain that while the TURDIS is as paradoxically large on the inside as the dimension-busting TARDIS, much of that useful extra space is taken up by what the Doctor can only describe as "literally mountains of other people's shit."
"It could really do with emptying."
Yet despite the obvious ignominy involved when one's mode of transport is basically a modified filthy plastic toilet, traversing time and space in the TURDIS is not without its lighter moments,
"The guidance system is all over the place," chuckles Who. "Half the time we don't know where we'll end up. There was this one bloke in Spain we materialised in front of - middle of nowhere it was - frightened the life out of him we did. But do you know what his first words to me were when I went over to apologise? "Buenas tardes senor." Even though I don't speak Spanish I could tell what he meant and I thought that was really nice of him."
A far cry indeed from the sorts of welcome the Doctor is used to receiving from villainous Cybermen and the like during his universe-spanning voyages.
"Anyway, you must excuse me," he says, "We've run out of sonic toilet paper again."
And with that, all the while trying not to gag, he disappears into the bowels of the TURDIS.
As the sign on the door changes from vacant to engaged there's a strange kind of "flushing" noise, a barely audible cry of "Cheerio!", and the noble Time Lord is gone once more - the only sign he was ever here being a yellowed square of flattened grass, and a pong that could floor a dalek.