Have just been drilling into a dividing wall in a 1936 terraced house in
London, to hang up a cupboard in the bedroom.

What I'm drilling into is almost like soft sand. I guess it must be some
kind of breeze block mortar that has deteriorated? The only thoughts I have
is to pack some polyfilla around the rawlplug to fill in the hole and get
some grip. Is that a good idea? Novice appreciates any advice on what best
to do. thanks.