Irish businessman Derek Quinlan has completed the deal to buy the 42-storey Citigroup building in London's Canary Wharf for about €1.4 billion.
Mr Quinlan bought the building in a 50-50 joint venture with UK private investment company Propinvest.
The deal is thought to be second largest single property deal ever in the UK.
Mr Quinlan, who formerly worked with the Revenue, is executive chairman of investment group Quinlan Private.
