Hi, Rusty!
I should perhaps I should think twice (or four or twenty ) times before wading in.....
although I think I am fairly calm most of the time, don't you think?
Like Rossim, I have heard of "as nutty as a fruitcake" meaning 'mad', but not 'cupcake' in that sense.
But looking it up in Chambers gives 'cupcake' as a small cake; an attractive woman ; a mad or eccentric person; or a term of endearment.
So Anne Bradford rules ok!
Did you see Peg's clue from the DM?
" Casual and dangerous in the east end (4)
Answered by Bernie as (h)airy.
So it's no longer just The Times coming out with "Londonisms".....!