|Attenborough was 29, and judging by photos, had not yet entered premature middle-age. Daniel Craig is 54.
Mrs. Boyle remarks that Trotter is rather young to be a sergeant. When filling in the guests on the backstory, Trotter says that the older boy would be around 22 now. As Delvino points out, the ages of Miss Caswell and Molly must move upward if he doesn't appear to be in his early 20s. The backstory involving the three of them, as well as Mrs. Boyle, is not supposed to have happened all that many years ago.
They can adjust some things in the script, but if the actor can't appear early 20s, well, I think it hurts the play. I like the play.