Turns it under the tiles is a backing board ... looks like asbestos cement too me !!!
So bagged the bit I pulled off and will dampen down and wear a mask disposable overallls to remove the rest
.Ok I know the area should be cone off the immediate area and evacuate the street .....
just don't tell parm 
The backer board Is just the bit behind the bath ...... hope you like the hardboard wall

