Metroline is a wholly owned subsidiary of Singapore based ComfortDelgro Corporation, which is the world's second largest listed land transport company. The purchase of Metroline was formally approved by shareholders on 21 March 2000.

Metroline’s principal business is the provision of bus services under contract to London Buses, operating through an area that extends from North to West London and includes Central London and the City. This expanded in August 2004 with the purchase of F E Thorpe & Sons Ltd.

Further expansion occured in November 2004 with the purchase of E H Mundy Holdings Ltd, which operated Armchair Passenger Transport Ltd.

During 2006 the coaching side of Armchair was amalgamated with the ComfortDelgro subsidiary Westbus. In January 2007 the F.E. Thorpes and the bus side of the Armchair business were absorbed into the main Metroline operation and these respective trading names are no longer used.