Hi Mikka
Thought the name sagwalla rang a bell, so did a bit of digging through some old books and came across this in 'Favourite Restaurant Curries' by Pat Chapman, published in 1988:-
"....'SAG WALA' Spinach Curry
Sag means spinach and wala means cooked (it also means a tradesman, eg, punka wala). This dish is more commonly referred to as sag bhajee but this name is used by the JHORNA, 32c High Street, Orpington, Kent for their recipe for this dish....."
So, now we know, Sagwalla is simply another name for a saag bhagee or bargee or however you want to spell it.
Regards
CoR