Thanks crafty and hippy. I've been to Portmerion and was a big fan of The Prisoner but it wasn't until I read Kafka that I realised where the idea had come from.
The obvious parallel is an apparently innocent individual being 'tried' by a shadowy burocracy for a crime of which he is unaware, with no-one willing to explain the reasons for his situation. Given current sophisticated levels of television, it is hard to imagine how genuinely exciting and unique 'The Prisoner' was when first shown in the late '60's - a true landmark of the genre.