Been a few times never came face to face with the security guard or been detected. Don’t think there is a dog but I know the route the guard takes and there’s only one so it’s easy to sneak round the grounds through a number of entrances. Mostly been in the lower gardens, play ground, tennis courts and the private entrance to walls hill ( a big field on a hill) but not inside because it’s all borded up and don’t wanna risk it because of the cameras. Haven’t been for a while because a group of people from my sixth form went and there was loads of legging it because the guard came and shouted at them and I was hesitant to go back for fear of tighter security. But don’t think there a security dogs, Hope this helps