I am at the Marylebone Farmer's Market at the very best time of day:  just before closing time. The get everything-practically-for-free time. 25+vendors are in the parking lot just off Moxon Road and are gathering their last remaining produce into crates and stacking them back onto their trucks. Most customers have left. It's a goldmine.

The fishmongers at maldon.co.uk yell over at me: "ALL FISH NOW HALF PRICE. GET YOUR FISH HERE NOW. ALL FISH…"

I walk up to their truck which features a...