Invalidation Of Insurance?

[jackthehat]

I have Googled but am getting conflicting information so I hope that some knowledgeable AB may be able to give me the definitive answer.

My parents live in a 2 bedroom apartment on the 3rd floor of a purpose built complex. On entering the flat, you are in an hallway off which are all the rooms. The open plan Kitchen/Living Room is furthest from the entrance door. All the rooms have solid fire doors with closers which means that the hallway is in permanent darkness. My parents are having a bit of work done to their flat soon and want to swap the solid door to the Living room for one which is substantially glass, thereby giving daylight to the hallway.

My Mum is concerned about invalidating their insurance were there to be a fire in the flat; naturally the Kitchen is the most likely place for this to occur.
The Buildings Insurance is paid for in their annual Management Fee, and their Contents Insurance simply states that they need to have a 5-lever mortice lock on the front door.

Can anyone advise me of the position their Insurance company is likely to take in a case of fire?

Many thanks.

[Peter Pedant]

I think you hvae to bite the bullet and say
Mama is right - taking down a fire door and replacing it with balsa wood may be relevant to a claim following a fire......

having said that
I have never had a fire in any property and
those fires caused by candles because the leccy was cut off v
I think they still paid out