What has happened between the Guinness family and Hamilton Osborne King? Last June the Dublin agency pulled off quite a coup when it sold Farmleigh, the Guinness mansion on the edge of the Phoenix Park, to the Government for a cool £23 million.

HOK has been retained over the years by the Guinness family to value its private properties but in a curious twist this week, the Iveaghs deserted their favourite agents and chose DTZ Sherry FitzGerald to handle the sale of their remaining properties in Castleknock. The sale involves three undistinguished houses and over 27 acres of housing land which were acquired over the years to form a buffer around Farmleigh. The combined properties are expected to make even more than Farmleigh, anything between £25 million and £30 million.

The Farmleigh sale was handled by HOK's Hugh Hamilton, the doyen of the country house market, who has since retired. Perhaps the Guinness family feel they are no longer locked in to HOK now that Hugh has bowed out.

When Farmleigh went on the market, one of the Iveagh trustees denied there were any plans to unload the remainder of the Castleknock property. But with huge money now available for house-building land, it is hardly surprising that the trustees have chosen this time to cash in their chips. Not that the Earl of Iveagh, 30, is short of a few bob. A recent study of the richest millionaires aged 30 or under put him at the top of the pile with assets of £600 million.

With the Earl now concentrating on his 23,000-acre Elveden estate in Suffolk, it will be no great surprise if he also decides to sell the family's remaining property in Ireland, a 700-acre cattle breeding farm near Ratoath, Co Meath.