Five people died and more than 80 were hurt when the train went through a red light and collided with another train outside Purley station, south London.

The accident involved the Littlehampton to Victoria train, driven by Robert Morgan, 64, from Ferring, West Sussex, and a Horsham to Victoria service.

Judges sitting in the Court of Appeal ruled Morgan's case was "arguable".

He was sentenced at the Old Bailey in September 1990 to 18 months in jail, of which 12 were suspended, after he pleaded guilty to two counts of manslaughter.

'Human factors'

His sentence was later reduced to four months on appeal.

Morgan's case centres on whether he would have felt constrained to plead guilty if what is now known about the causes of railway accidents was known at the time of his trial, and whether such information would have persuaded a jury to acquit him.

The appeal court judges said they had heard detailed submissions about infrastructure and human factors which may cause or contribute to an accident.

The court also heard evidence, previously not available, that the signal at the centre of the case "had been passed when on red" on four previous occasions between 1984 and 1987, and again in June 1991.

Fresh evidence to be presented at the forthcoming full appeal includes an expert's opinion that the driver made an error which was a consequence of the infrastructure design.

'Great public interest'

It will say that the root cause of the Purley crash was the "state of the infrastructure which existed at the time of the incident".

Lord Justice Maurice Kay said: "That conclusion is based to a significant extent on the evidence of the four incidents that preceded the crash in March 1989."

One of the reasons it was "appropriate" to give leave to appeal "so that the matter can be fully considered on another occasion" was the "great public interest" relating to such cases, he said.

Afterwards, Morgan's solicitor, Gary Rubin, said: "Mr Morgan is delighted that he has been granted leave to have his case heard by the Court of Appeal.

"We are now concentrating on fully preparing for the appeal hearing."

The appeal will be heard at a date to be fixed.