A group of six medals, including a Falklands War Distinguished Conduct Medal (DCM), are estimated to sell for between £100,000 and £120,000 at an online auction.
The medals were awarded to Sergeant (later Captain) J. S. Pettinger of 3rd Battalion, The Parachute Regiment.
Mark Quayle, associate director at auctioneers Dix Noonan Webb, said: "Over the years we have sold a variety of medals relating to the South Atlantic campaign, but this is one of the most important groups.
"A DCM is the most senior award, second only to the Victoria Cross."
John Stuart Pettinger distinguished himself on numerous occasions while serving as Patrol Commander D (Patrol) Company over 11 days of operations in and around the Mount Longdon area during the Falklands War.
D Company were tasked with close target reconnaissance in and among enemy lines.
They played a major role in giving descriptions of the enemy's strength and location ahead of the assault on Mount Longdon, with Sergeant Pettinger completing six close target reconnaissance missions.
The citation for his DCM states that he "acted as a guide for B Company" and was able to "place them in such a good starting position that the attack came as a complete surprise to the enemy".
Throughout the attack, he "was a constant source of information and advice to the company commander", it continued.
Mr Pettinger joined the Army as a junior soldier of The Parachute Regiment in September 1968, aged just 15.
Nearly 40 years after being awarded his DCM by the Queen at Buckingham Palace, he decided now was the time to sell the medals.
He said: "Now seems the right time to sell them to ensure that they are kept for posterity and the small part that I played in the Falklands War can be recorded for future generations."
The lot will be actioned by Dix Noonan Webb in their live online auction of Orders, Decorations, Medals and Military on 17 September.
It consists of the DCM; the UN Medal on United Nations Peacekeeping Force in Cyprus ribbon; General Service Medal 1962-2007 with a Northern Ireland clasp; the South Atlantic Medal 1982; Jubilee Medal 2002; and Volunteer Reserves Service Medal.
It also includes a written narrative that provides insights into Sergeant Pettinger's career and his actions during the Falklands War.
Cover image: The medals go on sale next month (Picture: Dix Noonan Webb).