When Luther comes in to interview Vivien Lake, he pours himself about 1 inch of water in a clear plastic cup. In the next shot he is walking with an almost-full cup.
Luther returns, and the clock on the wall reads 6.55 pm. During the same scene, a short while later, Luther's watch reads 6.30 pm.
In the scene where Luther is holding a gun to George Cornelius to get him to call the hit off, he cocks the revolver and points the gun at George's face. Then he hands the gun to George, and you can clearly see it is still cocked. However, when George takes it you can hear him cock the gun again.