Are rented properties required to have lockable windows?

I got my keys for my flat yesterday and have started moving in. I went to open my huge sash windows to discover that they had no locks on them. One in the bedroom has what looks like what used to be a lock at the top of the movable panel of the window but has been painted over so it has-been rendered unmovable/unusable. At first glance I had thought they had locks at the bottom because there were little metal public bathroom-style pins on the bottom of the movable panel but then came to realise these were to keep the window open as the hole to slide them into was part way up the window frame, there is no hole to slide them in at the bottom, and the windows are indescribably so they don’t stay up of their own accord. One of the holes doesn’t line up correctly so I can’t even keep one of the windows open, which is a pain, but my main concern is the fact there is no way to lock them.

I’m in a first floor flat if this makes any difference? I found it INSANELY difficult to pull up the window and lock it in place (to stay open) due to the sheer weight of it so I think someone would have great difficulty getting in but I guess if someone had a crow bar and something to keep the window open wide enough for them to get in it would be technically possible for someone to break in, especially as the door to the flat can be opened from the inside without any keys so they could leave that way. In addition to my own piece of mind I am concerned that I either won’t be able to get contents insurance or it will be very expensive due to there being no window locks. Should I broach the subject with my landlord?

sash locks can be bought and retro fitted. why not do that?

fit a 5 lever deadlock to door to your flat. This will probably be a requirement of insurance. However in case of fire you need to know where your keys are , so local councils do not like these locks and prefer euro thumb turns. ( thieves love them too)

My flat is rented and therefore, as I believe is the case with most other rental properties, there is a clause in my tenancy agreement that states I am not allowed to change any of the locks myself/am generally not allowed to do any structural changes to the flat without the landlord’s permission or I could lose my deposit. So I suppose my question was more about whether I had legal grounds to ask for locks on the windows as I have been given the impression that most landlords won’t change things for you unless it is absolutely necessary that they have to. And whether or not it’s illegal, does anyone think it’s worth approaching my landlord about/how should I go about approaching it with them? I’ve already had to give them an emergency call yesterday because the flush on my toilet broke and the cistern wouldn’t stop filling with water so am worried about giving them a bad first impression having to broach several things in the first couple of days, as I don’t want them to think I’m going to be a difficult tenant.

Idk whether this information will help but my front door has 2 locks, one that locks automatically when I close it behind me which the estate agent referred to as a “yale lock” (even though you can get several different styles of lock from yale and it isn’t even branded yale) and then another lock which has a British standard symbol on the outside of the flat and my estate agent described as a “mortice lock” but idk how many levers it has and am unsure how to check as that was all the info I could squeeze out of them, but neither lock can be locked with a key from inside the flat.

the plate on the lock usually tells you if its 3 lever or 5 lever. i am a landlord, if a tenant wanted to fit window locks I would not be bothered at all