River 'What' Edgware Middlesex

Unknown river in Edgware, Middlesex.
Having lived in Edgware a number of years I know of a few local rivers, streams or brooks. This one is a mystery, I haven't found it on any maps. It flows just West of Edgware Synagogue, a tunnel shows that obviously takes it under the A41 Edgware Way but from there I am not sure of its route.
It probably joins at some point to either Dean's Brook, a couple of hundred yards East, or maybe Edgwarebury Brook which is a similar distance West.
Normally water flow is very light, this video was taken after some rain.

[@BensWorkshop]

Often streams like that do get very overgrown.

[@send2gl]

Looked on a few maps, no idea what river this is or where it ends up.

[@BensWorkshop]

@@send2gl I can believe that.

[@Nick_80599]

That's the Edgwarebury Brook, there's several branches of it