Former Taoiseach John Bruton was among 38 new Irish and British knights and dames invested in the Sacred Military Constantinian Order of St George and Royal Order of Francis I at Westminster Cathedral in London.
The internationally recognised Orders of Knighthood are devoted to the promotion of the Catholic faith and undertake charitable, hospitaller and inter-faith activities at home and abroad.
The grand prior of the Constantinian Order, Cardinal Renato Raffaele Martino, and Archbishop George Stack of Cardiff concelebrated Mass at Westminster Cathedral for the new members.
The Order's Rome-based grand master, HRH Prince Carlo of Bourbon Two Sicilies, Duke of Castro, presided over the ceremony which was attended by 550 people including 60 knights and dames from across Ireland and Britain.
The President of Ireland and Queen Elizabeth II sent messages for the occasion.
Other new Irish members include Donal Downes, president of Association of Papal Orders in Ireland, and John Igoe, chancellor of Irish Association of the Sovereign Military Order of Malta.