Theory: Hannah and Dad met in Sheppey (or thereabouts)

Pro

At least two of Hannah's children (Paul, b. 1949 and Denise b. 1957) were born in Chatham. Chatham is about 10 miles from the Isle of Sheppey.

We know that at least part of Dad's National Service was spent on the Isle of Sheppey, due to a Newspaper clipping from this time, when Dad was a member of the Rugby team there.

According to a document that Steve has located (National Service discharge document), Dad's, National Service was from 13.04.1950 until 04.05.1952, although it is unclear when and how long he was at Sheppey

Contra

There is actually no concrete evidence to suggest that Dad even knew Hannah. Certainly her name has never been mentioned before, and suggestions that Dad knew her or met her are purely speculative