A rather pedestrian mystery, notable more for the confidence with which it deals with persons of exalted office than for any particular inspiration when it came to plot. First published 1980, and so I'm probably missing some context, not being very well up in any sort of politics of that era that doesn't involve trade unions. (They do feature in this, admittedly, but only very briefly.)

This rather fell into the trap of misdirecting so hard that none of the really interesting mystery stuff (When you know How, you know Who) got a look-in. The setting and characters seemed plausible, though.

http://www.bookcrossing.com/journal/988847