London-based Niall Wall (56) spent 10 years heading up his brother-in-law Paul Coulson's glass and packaging group Ardagh, which floated in 2017.
His wealth is derived from an 8.8pc stake in the business worth €196m, down from €356m after the share price plummeted by 45pc in the past year.
He chairs waste, water and energy firm Enva, which has operations here and in the UK, which is owned by Exponent, a private equity firm he's backed. He's also a director of Mayo man Frank Salmon's CMS Distribution.
He lives in a €6m home in London's Knightsbridge, and owns several properties on Dublin's Leeson Street as well as a house in Blackrock.