I'm not looking for legal advice. I live in a shared house. Each bedroom has a lock on the door. I keep finding keys in communal areas, for example keys in the bottom of a cupboards. The keys look like they're for the locks on the doors. I tested some keys on the door to my room and am wondering would it be legal to try to unlock other doors with the keys I found? I would like to know if the landlord is leaving keys to tenants rooms around the house because I wouldn't feel safe assuming he didn't leave a key to my room lying around. Normally I would ask but several rooms are vacant right now and others are on vacation etc.
No it is not legal; it is trespassing.
the common law definition of trespassing is to enter someone's land or property without their permission. By locking the door they have denied permission to everyone except those to whom they have given a key. If someone finds a key that happens to fit the lock, there is no longer a physical restriction but as they do not have permission, the legal restriction is still in force.