I suspect it will be every day they can get staff. It is interesting how they can staff that but one morning had to cancel some trains from Epsom due to a lack of staff. Obviously contingency guards wouldn't know the whole network and I don't t know which type staff were not avilable. I wonder which is the more popular stretch of line in terms of passengers, Guildford to Aldershot or Aldershot to Ascot? I'm suspecting the latter but I don't know.