New information has been revealed about the murder of a banker shot on his doorstep in the Highlands 13 years ago.

Father-of-two Alastair Wilson was fatally wounded in the shooting in Nairn in 2004.

His killer remains unknown and in a bid to solve the case police have revealed fresh details about the crime.

They say an envelope handed to the father-of-two minutes before he was shot was empty and it had the name "Paul" written on the front.

Police had refused to discuss the contents of the envelope, which was not recovered following the shooting.

On Monday, Mr Wilson's widow Veronica said his death had left a "dark shadow" hanging over the family.

"It would mean the world to us to have Alistair's killer brought to justice," she said.

"As a family, it has been difficult to understand why someone would do this to Alistair and it has been a dark shadow over us for the past 13 years."

She added: "Alistair was a loving, caring husband and father and nothing will ever change that.

"We cherish the time we had together, which for our boys was cruelly short.

"We will always remain hopeful that the person who killed Alistair will be caught and I would urge anyone who has information to come forward."

Police also revealed that a gun identical to the murder weapon - a rare German-made pistol dating back to the 1920s - was handed to police in Nairn last year.

It was given to officers in August following a house clearance and is believed to have been a war trophy from the Second World War.

Another similar gun was handed over in Nairn in May 2016 but neither is believed to be directly linked to the murder.

The officer leading the investigation into the murder, detective superintendent Gary Cunningham, has urged anyone with any information to come forward.

"We continue to pursue several lines of enquiry, one of which is the turquoise-coloured envelope that was handed to Alistair by the person who attended at his front door," he said.

"This envelope was the size that could fit a card and had the name 'Paul' on it. The envelope was empty and has never been recovered.

"As part of our re-investigation, we are in the process of reassessing all information and evidence available to us."

He added: "While we must protect specialist information that could only be known by the person involved, we believe given the level of debate around the envelope that it is in the interests of the investigation to release this new information."