The dangerous history of allotments

There are now thought to be about six million people interested in having an allotment, with waiting lists as long as 40 years in one London borough.  There have also been huge numbers of words written trying to explain their revival.
 
Perhaps the real question is why they ever went away, given the success of the Dig for Victory campaign in the Second World War, one of the most successful attempts to galvanise the public into action.