Astley Ainslie Hospital gate

I'm getting further afield on my daily walks, I'm glad to say and today I went through the grounds of this hospital which has lots of green spaces, trees and wildlife. It feels more like a park than a hospital in some ways. It's a rehabilitation hospital and was opened in 1923. I haven't been able to find out anything about the gates. There are several large houses on the site which pre-date the hospital and are still used to house administration and some outpatient services. It may be that the gates belonged to one of these houses, or perhaps they were built when the hospital was opened.