A NEWPORT man serving life for the murder of his ex-girlfriend and her new partner has launched a Court of Appeal fight to overturn his convictions.

Andrew Patrick Saunders, 22, stabbed to death Matalan workers Zoe Morgan, 21, and Lee Simmons, 33, in Cardiff's Queen Street in September 2016.

Prosecutors said Saunders had been upset at the breakdown of his relationship with Miss Morgan and planned the attack on the couple.

Saunders, of Walk Farm Drive, Castleton, was jailed for life for the double murder at Cardiff Crown Court in February last year.

But the Court of Appeal in London today heard that Saunders now claims he was wrongly convicted, because he was mentally unwell at the time.

Judges were told that fresh medical evidence suggests that Saunders was suffering from an "abnormality" of mind.

His barrister Winston Roddick QC said Saunders had suffered from an "adjustment disorder", which, if known at the time, would have changed his defence.

It would have allowed him to put forward a defence of "diminished responsibility", which could have led to manslaughter convictions, rather than murder.

"A characteristic of adjustment disorder is that the sufferer will appear normal and indistinguishable from others," he told the judges.

The case reached court today after an application by the prosecution to be able to instruct a specific psychiatrist to examine Saunders before the appeal.

But Mr Roddick contested the application, because the doctor had been previously instructed by Saunders and his team.

It meant he had already spoken to Saunders and the contents of their discussions should not be for the prosecution's eyes and ears.

There was a risk that any new report written by the doctor would be influenced by things told to him in legal confidence earlier by Saunders.

"This was a very young man, 20 years of age, being examined by a psychiatrist," said the barrister.

"The risk of him saying things that might incriminate him is greater than it would be if it were a mature male."

Refusing the prosecution application, Lady Justice Hallett said there was a risk the previous conversations would influence any new report.

And to allow the expert to be enlisted once again would be likely to result in more delay in a case which needs to be heard as soon as possible, she said.

"We are concerned about getting this application on," she told the parties.

"This case needs to proceed and, therefore, it should be listed as soon as a date is convenient to the court and to the parties."

No date was set for the appeal hearing, which is expected to last two days.