With Mary's escape from prison in 1568, Argyll became the leader of the Queen's Party, and led Mary's army in the defeat at Langside in which he showed little military skill. He continued to champion the queen's cause following her flight to England, but eventually reconciled with the regent Lennox in 1571, and lent his support to the King's party, as a means of restoring peace and lessening English meddling in Scottish affairs. He was appointed to the Privy Council that year, and became Lord Chancellor of Scotland in 1572.