In June 1976, Rolls-Royce acquired a 17% shareholding, but, in December 1977, the business was purchased by Hawker Siddeley.
In the summer of 1986, after months of denials, Perkins Engines purchased Gardner to complement their line of lighter diesel engines. Production then ceased until October, because Gardner's truck engine market share had slumped precariously, although Gardner's market for buses and coaches was doing better.
L. Gardner and Sons ceased production of new engines in the early 1990s. The introduction of emissions regulations for road-going Gardner diesels would have required the development of significantly modified, or totally new, engine designs, and in the marine market there was a shift away from big, low-speed, high-torque engines such as Gardners, towards adapted high-speed automotive turbodiesels.