Lodger Changes Locks without permission

Lodger moved in.

Upon 5 minutes of moving in he was told if he loses his keys he can go to my garage and retrieve a spare set.

3 nights later he lost his keys.

Go the the garage and retrieve the spare keys?

No.

He paid £250 for a locksmith to change the locks.

instead of going to the garage to get the spare set.

Scratching my head a bit with this one.

He was told prior to moving in a spare set were in the garage.

Maybe he has learning difficulties.

Maybe something is amiss here.

I was away from the property whilst he lost the keys.

He gave me two missed calls and then decided to take matters into his own hands and change the locks on my property without my permission.

I told him call me if you have any problems I will always pick up as soon as I can.

Phone was on silent when he rang.

He rang twice exactly in the space of 15 minutes.

One call at half past and another at quarter to.

Suspect something dodgy is going on here.

He was told that a spare set were in the garage.

Unauthorized guests who weren't meant to be there stole an extra set of keys from my bedroom whilst I was away?

Does he know this and got worried the place would get burgled so changed the locks to cover his tracks?

I really would appreciate some feedback on this, it seems really bizarre.

Thoughts anyone?

How would you guys feel if this was your property?

I made it clear from the outset that a spare set were in the garage.

Do you think it's acceptable to change the locks on your landlords property without asking them?