During WWII railroads were militarized. At the same they were allowed to continued operating under existing management. The nationalization the British railway companies happened after not during WWII. Rail companies were placed in a ticklish spot, they were still private corporations, they didn't want to complete annoy the traveling public who were past and future customers. So advertising was done by both government and railways to discourage consumer traffic.
Here is a flowchart that discourages email. It is not that email is such a bad thing but because it so useful. But too much email is sometimes worse that no email at all.
Flow chart after the jump.
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