Hat-tip to The Croydonian for this one.
Please visit his site – it’s excellent.

This from Hansard:

Mr. Hancock: To ask the Secretary of State for Defence pursuant to the answer of 29 September 2008…on Trident missiles, how many Trident warheads are either operationally available or undergoing maintenance.

Mr. Hutton: The UK has fewer than 160 operationally available Trident warheads. I am withholding further information as its release would, or would be likely to, prejudice national security.

“Each submarine [there are four] carries 16 Trident D-5 missiles, which can each carry up to twelve warheads. However, the UK government announced in 1998 that each submarine would carry only 48 warheads. However the working number should be in the region of 192“

Croydonian, as he so excellently puts it, does not think it likely that there are “warheads marooned in lost property or lapping the Circle Line”, but that “Hutton’s answer is an odd one, as I would expect the working figure to be in the region of 144, as one submarine is always being maintained while two are tooling around in harbour etc, leaving one to engage in a bit of silent running and generally keeping an eye on the bad guys du jour. So if 144 gives the game away, and 192 would not be credible, why ‘less than 160’?”

Mr C makes a good if rather scary point.