Since respect for the institution of monarchy prevented direct attacks on Charles, the alternative was to prosecute his 'evil counsellors'; in December, Parliament began the impeachment of Laud and Strafford, Holles' former brother-in-law. Although Holles viewed Archbishop Laud with hostility, his relationship with Strafford meant he was not involved his prosecution and tried to prevent his execution in May 1641. Instead he played a prominent part in negotiations with the Scots Covenanters that led to the Treaty of London in August.