New Bedroom with stud wall?

Hi Everyone, this is my first post, I hope someone will be able to help!

I have an unusual room in my flat and it's pretty large. I am aloud to install stud walls and would like to create another bedroom. I understand that if it's a habitable space, it will need another exit besides the door and also ventilation. I cannot put any new windows or doors in the existing walls so thought this might be the solution? I have included a rough drawing. The room will definitely be large enough for it, but I'm hoping for other people's opinions on the fire safety side of things. The large window opens up on to a flat roof just outside. I'm assuming that a door leading into the room and a window for emergency escape would be ok. I would have liked to just build a wall straight across the back of the room but there would only be one door and no window! Advice and opinions would be amazing!

What are the dimensions? That corridor is going to be long & dark.

It is for occasional use as a bedroom, or a main bedroom?

I certainly wouldn't do it like that, as you're wasting a huge amount of space. Post a plan of the whole flat, with dimensions

Space isn't the issue. The rest of the flat has nothing to do with it. Dimensions are not important at this point. This is to do with having the correct installation when it comes to fire hazards eg: having 2 ways of escaping in the event of fire.

Could you not do it with a bigger room and smaller corridor like this:

Ian H said:

Could you not do it with a bigger room and smaller corridor like this:
View attachment 165701

Click to expand...

That's exactly what I wanted to do, but In the event of fire there is only one exit. So to make it work, I believe I have to somehow Have another exit available. My latest idea is this:
This would mean you can exit the room in two places in the event of a fire. Not sure if this would be classed as a bedroom though!

A window onto a hallway? Are there no outside walls?