When is a watershed not a watershed?

The BBC have apparently received complaints (and have been slapped by OFCOM) because they showed Tarantino's Pulp Fiction ten minutes after the (9pm) watershed. Excuse me? What's the point of even having a watershed if you have to wait for sufficient amount of time before showing adult content! Perhaps we need to have layered watersheds, which allow increasingly extreme content as the evening gets later /sarcasm.