By Irish standards, IPUT is old money. Established in 1967, the Irish Property Unit Trust is the biggest owner of office buildings in Dublin.  But IPUT’s CEO Niall Gaffney is thinking bigger. His inspiration is the Grosvenor Estate, owner of the swanky London neighbourhoods of Mayfair and Belgravia.  The Grosvenor Estate has existed in its current form for 340 years, though it goes back even further than that. Asked by a reporter what he’d say to aspiring entrepreneurs, the Grosvenor Estate’s owner once said: “Make sure they have an ancestor who was a very close friend of William the Conqueror.”…