World War 2 saw rationing of food and other items in Britain. The war effort plus a blockade of imported food to Britain led to shortages.
Many foods such as bananas were not available. Other basic foods - such as meat, sugar and eggs - were rationed. The rationing system insured everyone had enough to eat and a nutritious diet, but it led to a more blander diet with many familiar items not being available. Christmas, a time when more food than usual is consumed, suffered with traditional Christmas items such as turkey, chocolate and many alcoholic drinks unavailable. Instead people had to make to with alternative Christmas foods substituting foods such as vegetable or oatmeal for meat products.
Try some rationing Christmas dishes with this book - Ration Book Christmas Cookbook.