Michael Cornish and family
Cornish, 63, owns half of a Welsh hydro-electric generating business but the Lincolnshire-based family's fortune came from Linpac, the packaging group that supplied McDonald's and was sold in 2003 for £860m. The family received £700m and reinvested £120m but when Linpac ran into trouble a US hedge fund started buying its debt. By early 2015 it had 85%, valuing the operation at £200m. The Cornishes' hit keeps them at £500m.