Justin Royston Thomas, of Llantwit Fardre, Rhondda Cynon Taf went far above and beyond the call of duty in 2003 when serving as a Royal Marine in Iraq.
Whilst his troop was under heavy fire including rocket-propelled grenades, he took a risk and climbed back into a vehicle alone, to return fire.
Using only a machine gun, he fought off over 100 insurgents allowing his troop, 40 Commando, Royal Marines, to re-group and avoid casualties.
This action earned the then Lance-Corporal a Conspicuous Gallantry Cross, the highest award for gallantry in the face of the enemy below the Victoria Cross.
Thomas said that whilst he was proud of his actions, he was more nervous about meeting the Queen.
The citation read "As small arms and RPGs landed all around him, his determination to suppress the enemy did not waver, nor did his courage in the face of considerable threat to his own life.
This singular act of selfless bravery ensured that his troop were able to extract safely from effective enemy fire without loss."
Now 30, and working as a civil servant, Thomas is considering other priorities.
He has one small child with his wife Heather and is hoping they will have more. He believes the sale of the medal, with a reserve price of £60,000 will help his family, notably by helping them buy a larger house.
Thomas, who has always had an interest in medals, explains "I'll be sad to part with it but I have to do what is right for myself and my family".
The medal, which will be auctioned together with Thomas's service medals from Iraq, Afghanistan and Northern Ireland in October, is likely to appeal strongly to collectors.
Not only is the Conspicuous Gallantry Cross prestigious, and so far has only been awarded 29 times since its introduction in 1995 (replacing equivalent medals), but the full account of Thomas's specific story will contribute to the value.