At the end of last week, my DNA results came through.
It seems that Tom's French & German DNA came from my side of the family after all, and I was delighted to learn that I have more French & German DNA than British & Irish. Don't suppose it entitles me to a French or German passport though!
Apparently, it's likely that I had a grandparent or great grandparent who was 100% French or German, probably born between 1860 and 1920. I've traced all except one of my great grandparents and they were all firmly rooted in Norfolk, and it looks like the last one was an 'incomer' from either Cardiff or London. I shall keep on going back in time...