Opinions on a lock on teenagers bedroom door

[lou4791]

I have a 15 year old DS who has taken it upon himself to fit a bolt type lock on his bedroom door. I really don't like it, find shouting through a locked door irritating and my gut feeling is to remove it, but I am aware of my DS's need for privacy. He says he needs it to keep out his toddler brother who interferes with his things and for general privacy. However, i'm sure he also wants it on so he can get away with screen activities late at night when everything should be turned off.
What are other Mumsnetters' opinions of teenagers being able to lock their bedroom doors?

I think that as long as your teenager can trust you not to go in his room when you promise you won't, and can trust you to knock before entering, then he shouldn't need a lock. The toddler should be taught not to go in the room. If he's old enough to go in on his own, then he's probably old enough to understand "rules".

However, if you've betrayed your teenager's trust by going in his room when you've promised not to, then I'm sorry, but you've made your own bed....