The company, which was set up in 1979 by managing director Michael Quinn, operates contracts to install and repair electrical equipment on London Underground and surface rail operations. The company turnsover around £29m.

Zeus Private Equity’s managing partner Gary Tipper, who has joined the MJ Quinn board, said: “This transaction allows MJ Quinn to move into its next stage of growth and capitalise on the volume of opportunities in the transport sector, thanks to its preferred supplier status with the London Underground.”.