Problems with John Duttine's aging in story

In 1929 Duttine's character says he has been at the school eleven years and soon after that he says he is 31 (at time of 1929 elections). If this is correct by 1939-40 when the story ends he is 41 or thereabouts. Yet, in his early thirties he is made to look like a man of 45 to 50 and by the end of the story he looks nearer 55 than 41. O.K. some people looked older in those days, but not that old.

It also seems unrealistic (I don't know Delderfield's books)that a working-class hero would ever have been allowed to become a headmaster of what is essentially an upper-class school in the 1930s let alone at the early age of 35 or thereabouts. The toffs were still closing ranks pretty much into the 1960s in the public school system. You will also find that being a brilliant teacher and having published a book would have been considered par for the course in those days. In the real world the average headmaster was in his early to late sixties then. It just does not ring true that someone from his background without having been to university would have been permitted to reach the level he did.