A German man's legal attempt to prove that he invented the Sony Walkman will cost the British taxpayer pounds 500,000 after his claim was thrown out yesterday by three Court of Appeal judges.

Andreas Pavel, 51, who spent a pounds 1m inheritance unsuccessfully fighting the Japanese multinational through the courts, funded the appeal with legal aid. The judges, who deplored the "inefficiency, delay and excessive costs" of the hearings, ordered Mr Pavel to pay the costs of Sony and Toshiba, which will all come from legal aid.

A spokesman for Sony said after the hearing that they had had to pay the pounds 2m legal bill of the Patents County Court hearing which ruled Mr Pavel's patent invalid in 1993.

Mr Pavel, who now lives in Milan, had hoped to claim up to pounds 100m in royalties from Sony if he had won his appeal. He now faces bankruptcy but both Sony and Toshiba said it would not be worthwhile pursuing him for any of their costs because of his lack of funds.

Lord Justice Neill, Lord Justice Hobhouse and Lord Justice Aldous all agreed that Mr Pavel's original patent was not an inventive concept and refused him leave to appeal to the House of Lords.

Guy Burkill, representing Sony at today's hearing, told the judges that Pavel had "no disposable capital" and there was no point in an order for costs being made against him.

Lord Justice Aldous said in his judgment that Mr Pavel's patent was for an invention called a "Stereophonic Production System for Personal Wear" on a belt, which was revoked by the Patents County Court in a hearing which began in 1990. In 1993 that court ruled that the claim was invalid because it lacked novelty and the idea was obvious.

Mr Pavel was not in court yesterday but is pursuing his legal battle against Sony in the United States.

News analysis, page 11