Stirling, based in Bristol, provides specialist engineering services and active control products for commercial and defence clients in the global aerospace and marine markets.
It was formed in 1987 as a spin-out of a university research department and employs more than 90 staff with a wealth of knowledge of over 70 different aircraft types and support to nine navies, worldwide.
Enact acquired a majority stake in Stirling from founder Bob Stirling in 2014 and was supported by the introduction of Mark Cook as executive chairman.
Stirling has subsequently grown by more than 15 per cent per annum in addition to returning the business to high levels of profitability.
This is the final exit from Enact’s first fund where other exits include the sale of the West Cornwall Food Company to Samworth Brothers and Excelsior Technologies to Mondi Group.
The integration of Stirling extends Assystem Technologies’ existing aerospace and marine/naval capabilities, notably in the areas of landing gear, fuel systems and simulation systems. Ed Ransome, investment director at Endless, said: “It has been a pleasure to support the remarkable story of Stirling over the last three years.
“The management team and employees should be incredibly proud of what they have achieved and we believe that with the support of Assystem Technologies as their new owners they will continue to prosper.
“Yet another South West business that delivers globally-recognised, best-in-class engineering expertise.”
Mr Cook said: “Stirling has a truly world-class engineering capability and the investment from Enact was the catalyst to unlock its business potential and deliver impressive growth in revenues and profits.
“The Enact team have provided the optimum balance of support and challenge throughout the investment period, but clearly a lot of kudos also goes to the staff and management of Stirling.
“They have adapted to significant change, adopted new strategies and applied themselves relentlessly to create a great UK company.
“Under the leadership of Assystem Technologies, I am confident the growth will continue and expand into new market sectors.”
Olivier Aldrin, chief executive of Assystem Technologies, said: “I am delighted to welcome the Stirling team within Assystem Technologies.
“Our aerospace and marine customers have now access to an enhanced specialist engineering expertise, combined with new scale and truly global capabilities.”
Enact and Management were advised by Grant Thornton (Simon Woodcock and Andy Rice) and TLT (Andrew Webber and James Webb). Assystem Technologies were advised by Clearwater International, KPMG and Napthens.