Now if Germans want to buy an erotic ebook they will have to "stay up late" or get up before 6am to buy them.

The bizarre rules are the same as those which have applied to German cinemas showing erotic films since 2002. The idea is that kids should not be allowed to see inappropriate adult content, but the idea has been extended to include ebooks.

Booksellers found flouting the new rules could find themselves receiving legal action by the government's Federal Department for Media Harmful to Young Persons.

A fine of €50,000 could be handed down to any retailer found selling erotic ebooks between 6am and 9.59pm, but it is more likely that they will receive a warning at first, given how recently the law has been extended.

Like most forms of censorship it is impossible to enforce after all, if you want to buy smut from all you have to do is buy it from a site located in a different country.