Firing frozen chickens into aircraft engines might not sound like much of a lucrative exercise, but for 3i Group it is an area of business that has made the private equity firm more than four and a half times its initial investment.

Element Materials Technology, which operates testing laboratories subjecting tiny samples of plane, pipeline and car to extreme stress, was bought by 3i out of Dutch engineering firm Stork for €150 million in 2010 before being sold to Bridgepoint for €900 million in late 2015.