Dealer John Dixon said he found the letters in a house in the Scottish city of Edinburgh, including one inviting a teen-age Nelson to serve on the HMS Seahorse dated October 28, 1773.

Another is an official seal of office from King George III and the Admiralty appointing Lord Nelson as Vice Admiral of the Blue Squadron on January 1, 1805, 10 months before he died while squadron commander.

"The seal comes with the embossed coat of arms and signatures of the Admiralty and is in mint condition," Dixon said. "He was in charge of the Blue Squadron when he died on October 21, 1805."

A third is a handwritten letter from Nelson thanking God for the recovery of an injured friend, Dixon said.

The correspondence is expected to be sold or put up for auction.

"I was clearing the contents of a house in the west end of Edinburgh when I came across the letters," said Dixon, of Georgian Antiques.

"I knew they would be of great interest and was asked by the owner of the house to act as his agent in safely selling the letters," he added.

No value has been placed on the documents but similar archives have fetched more than 25,000 pounds (36,000 euros, 46,000 dollars), according to experts.

It is not known how the letters came to be in the hands of the current owners, but they were originally owned by Sir William Augustus Fraser (1826-1898), the English politician, author and collector.

Nelson joined the Navy at the age of 12, became a captain when he was 20, and saw service in the West Indies, the Baltics and Canada.

When Britain entered the French Revolutionary Wars in 1793, Nelson was given command of HMS Agamemnon.

As a commander he was known for bold action, and the occasional disregard of orders from his seniors, helping him win battles against the Spanish off Cape Vincent in 1797 and at the Battle of Copenhagen four years later.

At the Battle of the Nile in 1798, he destroyed Napoleon's fleet and bid for an overland trade route to India. His next posting took him to Naples, where he fell in love with Emma, Lady Hamilton.

Over the period 1794 to 1805, under Nelson's leadership, the British Navy proved its supremacy over the French.

His engagement at Cape Trafalgar, off the Spanish coast, saved Britain from the threat of invasion by Napoleon and ensured his place in history as Britain's greatest naval commander.

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