There were no consequences because the Prime Minister didn't sue, both because Prime Ministers generally have more important and less embarrassing things to be

There were no consequences because the Prime Minister didn't sue, both because Prime Ministers generally have more important and less embarrassing things to be doing that testifying in court that they never stuck their penis inside a roast piglet for a funny photo during their adolescence (even if they didn't!), and because the authors knew how to word rumours and innuendo so that it probably didn't fall foul of libel law, and that a PM they knew personally would go all "I'm not even going to dignify that with a response" in response rather than spend the next few years pursuing a vendetta against them.