The Metrobus manufactured by Metropolitan Cammell Weymann in Birmingham, was the next volume purchase by London Transport of new double deck buses after the DMS. With LT running Metropolitans from the same manufacturer, they took a demonstrater on loan at the end of 1977. This resulted in a trial of 5 vehicles running in 1978/9 that was first succesul so orders were placed for a significant numbers that were progressively introduced from 1979. The production vehicles could be distinguished from the trial vehicles as they had smaller, Routemaster style, blind boxes. LT considered the MkII version by trialling a pair against Leyland Olympian, Dennis Dominator and Volvo B55 types. A third Metrobus MkII was also due for delivery as a MkIII prototype but never materialised, like the MkIII Metrobus itself. Apart from a number of single door MkII's for Harrow and a few secondhand vehicles bought from the north of England the LT fleet was all MkI with the asymmetrical widscreen design. The LT Metrobus fleet went on to total 1,485 with LT becoming the biggest customer for the Metrobus, even beating West Midlands Travel in whose territory the Metrobus was built. M331 ended its London sevice running for London General.