Until the 1960s, most grocery stores sold their chickens frozen because of the risks of bacteria causing food poisoning. But M&S believed customers wanted fresh products and began to explore safe ways of selling chilled meat, rather than frozen.
In order to keep meat fresh M&S invented the 'cold-chain' process. Chickens were chilled straight after slaughter, transported in refrigerated trucks, kept in refrigerated storage, and sold from refrigerated counters – all at four degrees centigrade. The entire cold-chain process was specially designed by M&S, and was unique at the time. This M&S news article of 1963 explains the idea behind it.
Sell-by dates were first used at M&S in 1970, several years before they became compulsory. This new innovation was designed to make sure that foods were as fresh as possible when they reached the customer.
An M&S employee remembers:
'I was 17 years old when I started work at Marks & Spencer in Stevenage 1973. I was so excited as I was going to work on the food section and it was such a joy to see all the lovely food coming in. We were very strict with the date codes and would count our chickens every day, I loved every minute.'
Bacteria - single-celled organisms that live on, in and around most living and non-living things. They are so small they can only be seen under a microscope.