The BBC's Carla Romano: Confidential documents found by a man out walking his dog

The papers also contained details of security arrangements of past Royal visits and the blood types and medical details of members of the family, according to the Sun newspaper.

The confidential folder, which also referred to 27 Royal visits and details of approved doctors and consultant specialists on standby in case of emergencies, was discovered beside a road on the seafront at Ayr, police said.

The BBC's Ed Meynell: "Security arrangements for 30 royal visits"

An Ayrshire and Strathclyde Police spokesman said: "We can confirm that we are in receipt of historical health board documents, the contents of which we are not in a position to discuss.

"Although the document is not recent there is obvious concern as to how it came to be in the public domain. We are currently investigating the find."

The Sun report quotes an unnamed man, who found the papers, as saying he could not believe what he was reading.

He said: "I now know the blood types and other medical details of 10 members of the Royal family.

"Many of the letters had confidential marked clearly across the top and bottom of the pages.

"There were also names of approved doctors and consultant specialists on standby during all the visits in case of emergencies.

"Although it relates to past visits, much of the information would apply to future trips."

Frightened at discovery

The man said he had been frightened when he found the documents because he knew they were secret.

"Whoever was supposed to destroy the information obviously didn't do a very good job," he added.

A police source told the Sun it was suspected that the documents may have been weeded out for destruction.

The Sun said the folder contained 70 pages, many of them marked confidential, about 10 members of the Royal family, including the Queen and the Duchess of Gloucester.

Police stressed that the records were not recent, but there is obvious concern over the possibility that they could have ended up in the wrong hands.