I wonder about the two year old that is with the Landys in 1911; she doesn't seem to appear again apart from a birth reg and the census entry. Could that be Maisie with a different name?
Frederica Haddon b Seacombe? She might be worth investigating.

Cal - no prisoners to Australia in 1930s I'm afraid.

(that stopped in
1868) He could have gone voluntarily of course.
It might be worth trying newspapers again for William Hagland to check the family rumours. I know Barbara has already looked, but maybe trying local papers, broad searches on that surname which may have been mispelled etc might find something?

Concocting the death in jail story sounds feasible if William scooted off to AUstralia. "Writing him off" so to speak.