Pret operates a bit like a restaurant. They build a kitchen in (or very near) every shop. You won’t find ‘sell by’ dates on their fresh sandwiches and salads. They don’t sell ‘factory’ stuff.
They offer their food to charity at the end of each day rather than keep it over.
Pret shun the obscure chemicals, additives and preservatives common to so much ‘prepared’ and ‘fast’ food. Their ingredients are delivered early every day. They don’t mind that fresh and fragile ingredients go off quickly – they start from scratch each morning.