The secondary investment follows 3i’s original investment in AES in 1996, and values the company at £100 million.

CEO Chris Rea, who founded AES in 1979, will retain a majority interest and control of the business.

Coinciding with the increased investment, Hamdi Conger, previously non-executive director, will become chairman of AES. Richard Bishop joins the board as a non-executive director, and Neil MacDonald, formerly finance director at international engineering group Firth Rixson, becomes the company’s new finance director.

Former leader of the Conservative Party, William Hague, remains a non-executive director.

The company’s management was advised by Deloitte Corporate Finance. Martin Jenkins, partner at Deloitte, comments: ‘AES has developed from a start-up 25 years ago to a business operating from over 60 sites in 30 countries, which is now the fourth largest mechanical seals company in the world with exports to 83 countries.’