Hi,
My 1 year old king charles cavelier is  due to get the snip soon!  He only has one testicle, so the vet has to take the other one away, which hopefully is just inside his body near the other one. She thought it might come down but it has not. Anyone else experienced this?

It can happen to any breed. To play safe you ought to wait another 6 months or so before neutering (18 months is a better time anyway) as there is still a slight chance the other testicle will drop -and the surgery will then be a LOT easier. It can be a case of the vet having to go "hunt the ball" and literally search all over which obviously makes the surgery more major.