The man who came up with idea of the personal stereo is threatening to sue Apple over the iPod.

Andreas Pavel filed a patent on the concept of a "stereobelt" back in 1978. The idea was for a small portable music player that could be clipped to a belt or handbag, and produce sound to be played back through headphones.

None of Pavel's prototypes reached market. Two years after he patented the idea Sony unveiled the Walkman. Pavel used legal aid against Sony in the UK courts in 1993 and 1996 but lost both cases.

Pavel has recently been offered several million euros to settle the outstanding disputes with Sony. Sony told The Independent that the long-running dispute, which has gone on for 25 years, was settled "in friendly agreement".

As a result of the payout, Pavel is now said to be considering suing Apple – although he may have left it too late. Patents have a shelf-life of 20 years; Pavel's was filed in 1978 – 23 years before Apple introduced the iPod.