Former chemicals manufacturer and supplier Peter Humphrey, 51, was jailed for 12 years by Judge Graham Cottle at Exeter Crown Court in March.

Babysitter Beverley Hammett, then 19, has undergone extensive plastic surgery on her face since the attack on 10 July 1996.

The trial jury heard how Humphrey hired an unknown man to call at his house in Devon, and injure his wife.

But 37-year-old Susan Humphrey was out and the man threw a jar of concentrated nitric acid at Miss Hammett when she opened the door.

Question of misdirection

Humphrey was convicted of aiding and abetting, counselling or procuring someone unknown to cause grievous bodily harm to Miss Hammett with intent to cause grievous bodily harm to Mrs Humphrey.

Humphrey's renewed application was heard in the Criminal Appeal Court in London on Monday by Lord Justice Buxton, Mr Justice Blofeld and Judge Martin Tucker QC.

After the hearing, Humphrey's solicitor, Jim McIntosh, said the appeal had been granted because there was a question of whether there had been a misdirection by the trial judge.

'Not very happy'

That would have to be considered at a full appeal hearing, together with certain aspects of the evidence, he said.

Humphrey would also be allowed to appeal against the length of his prison term, which he is serving in Parkhurst jail.

Miss Hammett's mother Val said from their home in Seaton, east Devon, on Monday that she was "disappointed" at the outcome of the appeal hearing.

"I am not very happy. We just want to get on with our lives really."