Is a fire door needed to protect private stairs within a two storey flat?

[Oliver H]

I have a flat which occupies the second and third floors of my building -  these are the top floors. I wanted to remove the door on the second floor that leads to the staircase which accesses the third (top) floor to allow more light to reach the landing. The third floor it is essentially a loft space, it has no doors except external doors that lead to a large (4x5m) roof terrace. The entrance to my flat is on the first floor.

Would it be against building regulations to remove the door to the top flight of stairs. I can install fire doors on all the other rooms in the flat?

I have attached some floor plans that show the door I want to remove in red.floor plans.pdf