Highbury Park

Below are the two sides of a small piece of paper. One side reveals it is probably a sixth or an eight of a document from the romanian consulate in Antwerp. There are several of such documents (in diffferent states of conservation) in the binder :

On the other side is an adress in London : 

which I read as

S Saperstein
125 Higbhry Park 5
London

very difficult to decypher beneath the line ; "11 Kay" ?

We know from this card that Eisik most probably went to London between 1922 and 1935. What does Internet research on the above name and address reveal ?
I assume that Higbhry is a notation of Highbury.

This brings us to "125 Highbury Park" (Also guessing that the "5 London" on the card stands for N5 today ):

Unfortunatelly I have not been able to look furhter what this adress reveals around the 1930's.