Reportedly the other actors were so stunned by the ferocity of Sir Ben Kingsley's performance that they occasionally forgot their lines and much of the fear in their performances wasn't difficult to act.
The boulder was made of fiberglass. A large net was kept open on the ledge of the pool so that if the boulder went over the pool, it would not continue down the hill into the village below. Additional shots involving the boulder were created digitally.
Ray Winstone travelled to Spain two weeks before filming commenced to get as deep a tan as he could in the time possible and to eat as much as he could to bulk up considerably. He called it "the best rehearsal time I've ever had in my life."
The conversation in the kitchen between Gal (Ray Winstone) and Don (Sir Ben Kingsley) originally took place in the living room, but Director Jonathan Glazer decided that a more domestic and less formal setting would be more effective. Also, the shot where Don kicks the cabinet doors was done in only one take. Glazer decided that coverage wasn't necessary.
Among the photos in Gal's bedroom is the publicity photo of Ray Winstone from the early nineties. It's best seen in the scene of DeeDee (Amanda Redman) laying in bed as Don (Sir Ben Kingsley) criticizes her in front of Gal (Winstone).
Even though it wasn't scripted, when Sir Ben Kingsley thought deeply about his character and where his personality came from, he arrived to the conclusion that Don was abused as a child, and played him with that in mind.