Extensive architectural plans of the Queen's official residence in Edinburgh, found last week by a dog walker, did not originate from the Royal household, investigators have claimed.

Subsequent investigation has shown that the drawings found by Polly, an inquisitive Jack Russell, were not in fact details of Holyrood Palace but plans relating to the Royal Mews and café located just in front of the Palace.

The plans relate to correspondence between architects and lawyers in connection with a licensing application for the café.

The letter attached to the drawings comes from Edinburgh architects Marcus Dean Associates, was dated December 29, 2008 and addressed to lawyers at Morton Fraser.

The architects' drawings included sizes of the gardens and specific locations for boiler rooms, gas meters, store cupboards, kitchens, lavatories and wash areas.

Three public entrances are highlighted, and the dimensions of the stable yards and seated terrace areas are also given.

Although this has been acknowledged as a serious breach in Palace security, sources stress that the plans, which centre around the café, are all accessible to the general public and do not include secure parts of the building in which the Royal Family stays.

The papers, alongside a covering letter, were discovered by Daily Record writer Joan Burnie under a bush on a public path leading to the water of Leith in Roseburn, Edinburgh.

“Polly came out with the plans in her mouth. I took them from her to see what they were and that's when I saw the letter,” Ms Burnie said.

“I was shocked… I reckon security has been breached.”

A spokesman from the Palace has admitted that the papers should obviously not have been found where they were and that the finding is being taken very seriously indeed.

However, the spokesman added that there was no cause for alarm as the Queen's security remains unthreatened.

The event adds to a long list of security issues for Holyrood Palace, which has been compromised on more than one occasion in recent years.

A Sunday Times reporter succeeded in overcoming all security obstacles to get within yards of the Queen's bedroom back in September 2004, and in 2006 a man successfully clambered over the fence, through some doors and up a staircase before demanding to see the Queen.

Despite the minor nature of the breach, it will nonetheless be embarassing for an institution which takes security very seriously.

Speaking exclusively to The Journal, a member of staff at the Palace, who wished to remain anonymous, detailed the extensive vetting procedures for applicants.

Staff are required to complete comprehensive security forms, providing addresses for all direct relations, as well as personal histories of their parents.

Assessment often takes a number of months. Photo security passes are obligatory for staff on site.

Royal aides have thanked The Daily Record for returning the plans to Holyrood Palace.