Concerned by the possibility of the snakes being venomous I had bought a couple of days ago the definitive text on the subject "The Herpetology of Nepal" by Dr T K Shrestha.
It didn't help much as many of the pictures were in black and white and the descriptions included statements like "the females lay eggs" and "the pupils are round". I wasn't going close enough today to find out the shape of the pupils of the snake in question but I imagine that they were fairly dilated. My best guess is that this is a common rat snake which is only aggressive when attacked, so sooner or later my dog Bryher is in for a shock.
Today marked the start of my two year old's sex education - "what is those snakes doing?" she asked. This must be Nepal's variation on the birds and the bees.