Five get a convincing explanation
Camping and tramping fiction shared an assumption that the entire British countryside was a safe playground for middle-class youngsters. The background to that assumption was the great agricultural depression which began at the turn of the century and which left rural England almost empty. Since the First World War the young had left the countryside in their thousands, leaving a beautiful and rather run down rural landscape. This was infintely appealing to the middle classes, who could see it as a lovely playground full of history and mystery, and suitable for hiking, boating and all manner of adventures for children.

The rural background to all those friendly and welcoming fictional farmers was, in reality, one of economic and social stagnation in which farmers had to supplement their incomes in any way they could. When farmers began to prosper and agriculture became intensive, an entire of genre of children's fiction was effectively wiped out by Common Market farming subsidies. And at about the same time the Beeching cuts closed down the branch lines that had taken so many fictional children by steam to their favourite holiday destinations.

Victor Watson Reading Series Fiction (2000)