Loosestrife

Lysimachia vulgaris, most likely. Google Lens is good at plant id. 

The bus trip for the day was to find a 47 at the Bread Street stop (which isn't on Bread Street, but on Lothian Road close to the Bread Street corner) and have it drop us at IKEA halfway to Penicuik down the A701.  It's a sufficiently frequent service that we didn't have long to wait in either direction. 
Did survey on the showroom; now I know what 'oak effect' looks like, compared to 'oak', or 'oak veneer'. We were ready for tea and fikka by the time we'd done that one floor. The loosestrife was flourishing by the return bus stop.

Walk by the canal later in sunshine.