Yesterday in BA 675 (IST-LHR) departing at 10:00 they only served breakfast. According to this guide, shouldn't they have served the "rest of the day" offering?
There's a note about this in
Prospero's post above, but IST is a exception to the usual timetable - it's a night stop that leaves unusually late in the morning, due to a combination of the crew rest requirement and the 2 hour time gap between LHR and IST. So consequently they serve the small tray night stop breakfast and relatively late in the morning.
Prospero notes that this is perhaps insufficient food for a trip of this length, so if you have been on this sector recently you may want to provide feedback along those lines.