Memories triggered by smells seem to be more powerful than others.
My first, from late 1930s, is of the yeasty aroma from the 3 breweries in Cambrian Road, Newport. Although they're long gone, I still see Cambrian Road whenever I pass a brewery.
The smell of a steam locomotive (rare these days) brings back memories from a couple of years later, standing with my Grampa on the railway bridge, watching wagons being shunted below.
But the most persistent, surprisingly, is from 1955. At college in the east end of London, I took the tube to Wapping station to walk to the "Prospect of Whitby". The narrow cobbled streets and the towering spice warehouses on a cold, damp November evening - I still see the scene (now much changed) whenever I open a jar of spice.