[3] In an interview with the International Herald Tribune in January 2009, Seán Dunne commented "if the banking crisis continues I could be considered insolvent.
"[4][5] In 1990, Dunne was involved with the development of lands at St Helens in Booterstown, Dublin through Berland Homes company, of which he was managing director.
[6] After higher stamp duty rates were introduced in September 1990, Berland was forced to reduce the price of houses by up to 10% in order to increase sales.
In 1994, Dunne along with fellow Berland directors, David Shubotham, James Burke and Frank Belton sought to build 200 apartments in the grounds of St Helens.
Rebecca Jeffares of St Helen's House Preservation Group had previously prevented an office development at the site in 1992.
[10] In May 1997 Dunne bought Woodtown Manor and 150 acres in Rathfarnham, Dublin from Guinness heir Garech Browne for around £1.4m.
[12] In late 1997, Dunne was involved with the Anna Livia Consortium, which hoped to win the competition to build a national conference centre at Grand Canal Dock.
[13] The same year, Dunne through Mountbrook Homes and Sean Mulryan through Ballymore properties, bought a 100-acre site south of Greystones, County Wicklow.
[citation needed] Dunne's plans to build Ireland's tallest building,[21] a Dubai-style office tower in the shape of a diamond with a one-billion euro price tag[19] created a political tug-of-war in Irish society between those who saw it as a blot on the traditional Irish architectural landscape, represented by 37 separate political groups, and those who saw it as a welcome sign of modernity, represented by 90 groups who have filed appeals on Dunne's behalf.
[22][23][24] Although Dunne's high rise development was approved by the planning authority, An Bord Pleanála, the decision was appealed and rejected on 30 January 2009.
[26] As of November 2010, Seán Dunne faced difficulties regarding a multi-million dollar property in an exclusive estate in Greenwich, Connecticut.
[27][28] In July 2011, the National Asset Management Agency (NAMA) appointed receivers to some properties controlled by Dunne.
[29] As of March 2012, Dunne faced the prospect of bankruptcy after he agreed to court orders directing him to repay more than €185 million to the National Asset Management Agency.
In 2004, Dunne married Sunday Independent gossip columnist Gayle Killilea, whom he met at the Galway Races in 2002.