Greenhill, the boutique investment bank, is joining four private equity firms to buy a stake in a $1bn (€759m) start-up insurer.

Greenhill bought a 30% stake in Ironshore Insurance, a newly formed startup insurer that is based in the Cayman Islands. It is capitalised with over $1bn in private placement money from a group including Bear Stearns Merchant Banking, Lazard Alternative Investments' Corporate Partners unit, Fremont Partners and TowerBrook Partners.