The Lord Lieutenant possessed a number of overlapping roles.
- the representative of the King (the "viceroy");
- the head of the executive in Ireland;
- (on occasion) a member of the English or British Cabinet;
- the fount of mercy, justice and patronage;
- (on occasion) commander-in-chief in Ireland.
- Grand Master of the Order of St. Patrick
Prior to the Act of Union 1800 which abolished the Irish parliament, the Lord Lieutenant formally delivered the Speech from the Throne outlining his Government's policies. His Government exercised effective control of parliament through the extensive exercise of the powers of patronage, namely the awarding of peerages, baronetcies and state honours. Critics accused successive viceroys of using their patronage power as a corrupt means of controlling parliament. On one day in July 1777, Lord Buckinghamshire as Lord Lieutenant promoted 5 viscounts to earls, 7 barons to viscounts, and created 18 new barons.:66 The power of patronage was used to bribe MPs and peers into supporting the Act of Union 1800, with many of those who changed sides and supported the Union in Parliament awarded peerages and honours for doing so.