part of our Regs mean that we are supposed to have a minimum 11 hours between shifts for a normal duty, 8 hours in 'extingencies of duty' (ie things have gone tits up) the other part means that we are required to stay on duty until the job we are dealing with has concluded unless it is reasonable to hand it over. In reality most people just bite the bullet and get back in for the normal start time as it saves on grief, even if that does mean only a few hours kip in between shifts. The problem with working 12 hours shifts in those instances is if you have a serious incident such as first on scene for life threatening gbh or a murder then you are there until you have done everything possible to hand over, which is why everyone on my team has done at least a couple of shifts in excess of 20 hours in the last year, though thankfully they aren't that often. 14-16 hours happens quite a bit though, especially day going into night, they hurt after a while!! And before someone says, yes we (Police) do get paid overtime after the first half hour, but the vast majority of the time, sleep is better than pay!