Born and raised in England, Joey Chapman, the son of a working-class shipbuilder, was attending art school when he became friends with Kenneth Crichton, the heir to Lord Montgomery Falsworth. While visiting the Falsworth estate, Joey discovered that the aged Lord Falsworth was once the British hero Union Jack - and that Falsworth had enlisted the aid of his wartime ally Captain America to fight the menace of his vampiric brother, Baron Blood, who had returned from apparent death. Montgomery tried to lure Blood into an ambush, using himself as bait, but suffered a heart attack; aware of the vampire's impending arrival (disguised as the local doctor), it was decided that Joey would take his place (as he was stronger than Kenneth). Wearing the Union Jack costume, Joey helped Cap destroy Baron Blood once and for all. Lord Falsworth died of a heart attack shortly thereafter, leaving Joey to carry on his heroic legacy.

The new Union Jack continued to fight evil, both alone and as a member of the Knights of Pendragon and the new Invaders. He frequently battled vampires, including the Baroness Blood, who carried on for the Baron and caused the death of Joey's friend Kenneth Crichton. After being mortally wounded, Kenneth's mother, Lady Jacqueline - once the WWII-era super-speedster known as Spitfire - regained her youth and powers through a blood transfusion from the original Human Torch. She and Joey grew close and began a romance, but the difference in their ages and backgrounds was too much to overcome and they broke up. However, they remain friends and allies.

Currently, Union Jack works alone, though he makes himself available to the British Secret Service agency MI5 when needed, and is always willing to help friends and allies like Captain America.