Jim Mansfield's property portfolio has been valued in recent weeks at €1.7 billion. This represents a €300 million increase on the €1.4 billion valuation placed on Mr Mansfield's extensive landbank as recently as 2006.

He owns more than 2,250 acres of land in Dublin and Kildare, including the Citywest Hotel and golf resort in Saggart, the Westin aerodrome near Lucan, the West Park Hotel in Dublin and the PGA National golf course at Palmerstown House in Kildare.

Mr Mansfield's portfolio also includes 225 apartments in Saggart, which are used by his Citywest complex.

"All of our properties are within a bicycle ride of each other," Mr Mansfield told The Irish Times. "We have never received a single cent in grants."

Mr Mansfield bought most of the land at Citywest for just over €1 million in 1990. "This success is all down to good planning, foresight and hard work," he said.

Mr Mansfield also confirmed yesterday that he spent €240 million in 2007 on acquisitions. This included spending more than €20 million buying Finnstown Country House Hotel in west Dublin and adjoining lands from the Hickey family.

He also paid about €32 million buying 11 acres of land adjoining Citywest from well-known folk singer Paddy Reilly.

Bernard O'Byrne, chief executive of the Mansfield Group, described the recent valuation as conservative. It reflects the downturn in the property sector and concerns about the Irish economy.

"I would say the true value is well in excess of €2 billion," Mr O'Byrne added.

The increase in the valuation of Mr Mansfield's property assets reflects an expansion of his landbank and a rezoning of the Palmerstown House site in Kildare.

This land was rezoned for tourism and recreational activities and Mr Mansfield is seeking planning permission from Kildare County Council to build a 200-bed, five-star hotel and a large number of residential units there.

He was recently granted planning permission from South Dublin County Council to build a 4,000-capacity conference centre at Citywest, although this could be appealed to An Bord Pleanála.

The Mansfield Group employs more than 1,300 staff and made profits of €28 million in 2006 on turnover of €108 million.

Mr Mansfield has just spent €44 million adding 452 new bedrooms to the Citywest complex. "We had an extremely busy 2007 and these additional rooms come at a time when the hotel badly needs them," Mr O'Byrne said.

"This investment is not tax-based - we simply need the additional capacity - especially now that the Burlington Hotel has closed."