go to your local builders and ask for a bag of easy fill
It's 5 inches deep!
Easyfill wont do it!
Its above a door or opening so maybe a rotten timber lintel?
Fill it with a pornographic magazine, pack those pages in tight. Then skim with pig excrement modified with SBR, If still not smooth enough then you can fall back on your full bag of easyfill. :RpS_w00t:
you dont need to skim over the easy fill...........just bang it in. leave it proud of the wall so when you rub it up it will finish flush with the wall. unibond the hole prior to filling for suction control purposes. or expanding foam to reduce the depth of the hole to fill if u like............