Atonement may have been a romantic drama but it was also a war film, notably filming scenes of the war front on Dunkirk beach. And, unlike a film such as Dunkirk, the movie didn't have a big budget to fund these scenes for more than two days of shooting (Notably in paying the 1000+ extras used). So, to pull off these scenes, director Joe Wright and cinematographer Seamus McGarvey were forced to reduce the shooting down into a 5½ minute long-take following James McAvoy's character as he moved a quarter of a mile along the beach. This was done by using the first day, and part of the second, to blocking and rehearsing the sequence until the sun was in the correct position in the afternoon ready to shoot.
Luckily, the shot took only 3½ takes. Why did it take ½ of a fourth take? This was due to the fourth take being abandoned mid-flow due to the lighting becoming too bad for shooting so the third take was used. Steadicam operator Peter Robertson is credited in accomplishing this scene by moving from a tracking vehicle, to on foot, to a rickshaw via a ramp and back to on foot. Suppose it fits the feeling of war as the shooting sounded, no doubt, chaotic and involved a lot of luck to survive! Stay tuned!