James was now acting head of the main branch of the powerful Douglas family and was left to maintain their influence in southern Scotland.

His successes in this regard preserved Douglas influence until the return of his elder brother from captivity in 1409, at which time he assumed the role of councillor and was rewarded with the grant of extensive estates.

In the early 1420s James acted as the link between his brother, the earl, and the powerful Murdoch Stewart, Duke of Albany.

In 1426 as a reward for his loyalty Douglas received royal confirmation of his lands and his eldest son William was knighted in 1430.

These events culminated in what would become known as the 'Black Dinner' at Edinburgh Castle, where his great-nephew William Douglas, 6th Earl of Douglas, 16 at the time, and his younger brother David were summarily beheaded on trumped up charges in the presence of a protesting young James II.