BOAC;
PJ - the only comment I have is my surprise when I was firmly informed by a couple of BA guys that in a lot of cases 'breaks' are rostered and mostly not interfered with.
Well, there may be some justification for this approach, based in the research on fatigue, sleep patterns and brain activity and the fact that none of us are the best judge of when we are fatigued or too groggy (after a deep-REM sleep during the break - we know that is to be avoided) to be in the seat right away. So I can understand if an organization has rostered breaks based upon these understandings if that's why and how it's done.
That said, just like any scheduling activity, by definition such does not take into account variations in circumstances and I think, within reason, crews should have the freedom to alter rostering schedules, followed by an air safety report so that reasons can be trended and modifications made to such rostering requirements.