The Queen and the President of Ireland stood side by side to observe the Irish Anthem being played by a military band in Windsor, during the first visit to the UK by an Irish head of state.
The anthem was played after the President Higgins and Michael Higgins were honoured with two separate gun salutes, and Mr Higgins and Philip inspected troops of the Queen's Company, Genadier Guards.
Major Andrew Seddon, captain of the Queen's Company Grenadier Guards, invited Mr Higgins to inspect the guard of honour, speaking to him in Irish. The Irish Guards was represented by their regimental band as the troops are currently on peacekeeping duties in Cyprus.
President Higgins presented a new ceremonial red coat to its regimental mascot, an Irish wolfhound called Domhnall of Shantamon.
Michael Higgins is the first Irish President to make a state visit to the UK, ending the day with a state banquet at Windsor Castle.
Today's historic visit is a symbolic ending to the painful separation of British and Irish states, but 3000 unsolved murders remain.