I remembered my Granny talking about Durtnalls when I was a wee small, so I asked my mother about it.
Durtnalls were a building firm. They built my Granny's house. She may even have been pally with some member of the family. My mother went away and checked the local phone book and- guess what- Durtnalls are still in business and still operating out of Brasted in Kent.
Jolly good show!