And Hayling Island author Pauline Rowson fears the information will now be withheld until 2030 at the earliest.

On February 12, 1959, Mrs Rowson's great-aunt Martha Giles was found dead on the bowling green of Wolverhampton's New Cross Hospital.

The nurse had been due to work a night shift on February 11, but on her way to work she was battered with a rock and stabbed in the heart and lung.

The murder caused an outcry and was given national media coverage, but the 45 year-old's killer was never brought to justice.

Mrs Rowson, 52, whose popular crime novels have been published in the UK, US and Poland, thinks the murder may have subconsciously inspired her crime-writing career.

She said: 'It was something that was talked about a lot when I was a child but then I think the adults in the family decided to stop, because it caused strain for them.

'Although it wasn't something I really thought about until relatively recently, I do wonder whether it planted the seeds of my interest in detective fiction. It could have been the inspiration.'

Her interest in the case was renewed last year, since when she has been trying to unearth its hidden secrets.

She said: 'I was asked if I'd ever experienced crime, and started to think about Martha. I wanted to see if we could find out more about what actually happened.'

She had hoped to mark the 50th anniversary of the crime with some solid leads, but a Freedom of Information request to the National Archives, where documents relating to the case are held, was turned down.

In rejecting her application, the archives' FOI officer said: 'There remains a possibility, however remote, that this case could be opened for reinvestigation at some point in the future.

'It is not in the public interest to jeopardise a prosecution for murder by releasing information that could be of later significance.'

Mrs Rowson said: 'It's very disappointing.

'I've got newspaper coverage of the murder and spoken to some of the officers involved at the time, but this is like hitting a brick wall.

'They say the possibility of reopening the case is remote and nothing has been done in 50 years, so it's very disappointing.

'I won't give up, though, and I am planning to try an appeal, as well as contacting my MP.'

Anyone with information about the murder can contact Mrs Rowson at pauline@rowmark.co.uk, or call (023) 9246 1931.