Mould inside stud wall

[a72o1]

I've been decorating the inside of a room which backs onto a bathroom.

Long story but it turns out there was a leak about 9 years ago from a bath waste pipe. The previous owners tried to repair themselves.

Part of the skirting is rotten. I've removed it and found several inspection holes cut in the plaster behind it. Looking inside the stud wall there is mould inside.

Given the age is this something to be concerned about?

 

[flameport]

Mould is a health hazard and it needs to be removed.
Unfortunately the only way to remove mould on plaster / plasterboard is to remove the whole lot and replace with new.