Background: Sir Anthony Joseph Francis O'Reilly, AO (born 7 May 1936), is an Irish former businessman and international rugby union player. He is known for his involvement in the Independent News & Media Group, which he led from 1973 to 2009, and as former CEO and Chairman of the H.J. Heinz Company. He was the leading shareholder of Waterford Wedgwood. Perhaps Ireland's first billionaire, as of 26 May 2014 O'Reilly is being pursued in the Irish courts for debts amounting to EUR22 million by AIB, following losses amounting to hundreds of millions of euro in his unsuccessful attempt to stop Denis O'Brien from assuming control of Independent News & Media.
Context: A number of homes are associated with O'Reilly, including his current official main residence, Lissadell, with a beach within private gated community Lyford Cay near Nassau in the Bahamas. For many years his principal residence and later a major base, was Castlemartin, a "big house" dating in current form from the 18th century, at Kilcullen, County Kildare (which has associated stud farm and cattle breeding premises on the large estate lands). O'Reilly purchased Castlemartin in 1972 from the Earl of Gowrie, and spent millions on improvements to the house and on restoration of the 15th century Church of St Mary in the grounds. On 15 February 2008 permission was granted for developments of two ancillary houses on a remote part of the estate, adjoining Kilcullen (Bridge) village's main street, incorporating residential, restaurant and retail space. In October 2007, O'Reilly paid a record EUR125,000 per acre for 60-acre (240,000 m2) Hollyhill Stud in Carnalway near Brannockstown, under 3 kilometres from Kilcullen. The stud farm on the banks of the Liffey, with a 10-room house and a cottage, was thought to have been intended for one of his daughters. In late 1995, he and his wife purchased a former solicitor's office, a four-storey Georgian house on Fitzwilliam Square, Dublin, with a courtyard and coachhouse with separate entrance. The 1 million Irish pound house, formerly owned by railway pioneer William Dargan, was a base when travel to Castlemartin was not feasible, and a place for meetings and his private office. O'Reilly also has a holiday compound, Shorecliffe, comprising several houses, garden areas and two swimming pools, by the sea in Glandore, County Cork. The O'Reillys also owned a chateau "built on the ruins of the castle where William the Conqueror plotted his 1066 invasion of England" at Deauville in France. For many years a key O'Reilly residence was a 34-room mock Tudor house of 8,000 square feet (740 m2) at Fox Chapel, Pittsburgh, with 7 acres (28,000 m2) of grounds. This property, his second home in that area, with eight bedrooms and bathrooms, an "Irish bar" in the basement, tennis courts, Japanese and English themed gardens and swimming and tennis facilities, was sold for around $US2.4 million in 2000 The residential complex in Glandore, the house on Fitzwilliam Square and the Castlemartin Estate have all been placed on the market in recent years. CANNOTANSWER
Question: what was his most important attribute?

Answer:

developments of two ancillary houses on a remote part of the estate, adjoining Kilcullen (Bridge) village's main street, incorporating residential, restaurant and retail space.