This is the first of only 2 films in the entire series to temporarily break chronology by opening with a flashback, to an event that took place in 1810, which puts that particular mission between 'Sharpe's Eagle' (1809) and 'Sharpe's Company' (1813).
The other one is 'Sharpe's Challenge', which opens with a flashback to 1803 (long before 'Sharpe's Rifles', taking place in 1809), then jumps forward 14 years for the rest of the movie (3 years after 'Sharpe's Waterloo').
This episode takes place in 1810 and 1813.
Sgt. Pope kicks Sgt. Harper in the face to end their first fight. When Andrew Schofield went to do this, his planted foot slipped on the wet ground and he accidentally kicked Daragh O'Malley for real, fracturing his cheek. O'Malley had to be rushed to the hospital for surgery and the injury took a few weeks to heal; since they couldn't delay filming, Harper's toothache was written into Sharpe's Siege (which was being shot at the same time) to explain O'Malley's swollen face.
Indoor scenes were filmed in an old carpet warehouse in Antalya, Turkey. Night scenes were filmed with windows blacked out, and the stifling Mediterranean heat made conditions very uncomfortable for the actors.
The masked phantom' character of the deformed Maj. Pyecroft and his love for the gypsy girl can be seen as an allusion to the 'Phantom of the Opera'. The musical had premiered some ten years earlier (in 1985 (London, West End) / 1986 (New York, Broadway), but is based on the much older original French novel "Le Fantome de l'Opera" by Gaston Leroux.)