In message , Roland Perry
writes

What that doesn't tell us is what was there before the 1930's and it
would be necessary to look at some old maps of the area.

Bartholomew's Handy Reference Atlas of 1925 shows the newly built North
Circular passing OVER the canal on a fairly narrow bridge (the North
Circular at that time was a rather modest road running from SW from
Golders Green - it simply petered out at Park Royal).
--
Paul Terry