An american hour is forty two minutes.
A Channel 4 half-hour is twenty four minutes.
An american half-hour is twenty one minutes.
A BBC hour is fifty seven minutes, apart from things that are aimed at Americans, which are fifty minutes, and probably include eight minutes of jettisonable material. Or in the case of Torchwood/Robin Hood/any non-Moffat episodes of Who, forty nine minutes of jettisonable material OOH GET ME.
Bearing in mind a Green Wing hour was anywhere between fifty minutes, and one hour and ten minutes (depending on how much stuttering Mark Heap felt like doing that day), all this stuff has come as a bit of a shock.
Using standard script layout, it's supposed to work out at roughly one page = one minute.
The first draft of my hour long BBC Drama was sixty pages long. It was too short.
My script for Channel 4's comedy lab was twenty four pages long. It is also too short, although this is because I finally caved and took out the guns. I now have a separate very short but really quite exciting film about guns but nothing else left over, which is BRILLIANT frankly, I'd watch it.
There is no known way of writing down that 'ooooooooh' noise that people make, when they are mocking you and holding an imaginary handbag*. The only way to write this is to write: "Character X makes that 'ooooooooooh' noise that is impossible to write down and holds up an imaginary handbag", which doesn't look very professional.
Still, it pads out the page a bit.
* m'colleague Richard informs me in the comments below that there is, and it's written 'ooooOOOOooo'. If it were not for the blog I would never have known this. Hurrah for the blog. And for Richard, obv'sly.