[Phil Masters]

This skill seems to get a fair amount of use in Ankh-Morpork City Watch Discworld demo game I've run at a number of conventions over the last year. Basically, it serves as the "knowing how this stuff is likely to go, if this is a normal investigation" skill when a bunch of Watchmen are trailing round the city (at worst, the "drop broad hints to clueless players" skill). It's the body of knowledge that lets a working copper handle routine criminal investigations without wasting too much time.

Of course, it's most fun when three PCs roll it, two of them make the roll, and the one who doesn't happens to have the highest Watch Rank.