In the aftermath of World War I, with millions of lives lost and Britain in financial tatters, extravagant pre-war gardens were untenable. Not even the royal family could justify such opulence. Out of practicality, people moved towards lower maintenance gardens.
When World War II broke out, a second blow hit the horticultural world. The labour force - already half of what it had been before the World War I - was called up again. Suddenly there were more pressing matters than gardening and all available land, including the Royal Parks, was turned over for growing food.