English: The Big Bus Company bus EM852 (reg. A852 SUL), a 1983 Leyland Titan (B15), pictured outside Westminster tube station, London, operating their 'blue route' sightseeing tour. It's making a left turn from Parliament Street into Bridge Street, to head over Westminster Bridge.

The 912th production Titan, it's from the later batch built at Leyland's expanded factory in the Lillyhall Industrial Estate in Workington (earlier ones were built by British Leyland subsidiary Park Royal Vehicles in Park Royal, London). As with the vast majority of production, it was delivered new to London Transport as part of the dual-door T-class, allocated fleet number T852.

On privatisation it passed into the fleet of London Central.

Having been sold around July 1998, by January 2001 it was with The Big Bus Company, who had bought it via Allco Passenger Vehicles and converted it to an open top bus, also removing the centre door.

In 2009 it was exported to the City Sightseeing franchise in San Francisco, USA, for further use as a tour bus. For the North American market a door in the offside was added, and the upper deck front windscreen was reduced to half its original height. It enetered service in San Francisco still wearing the maroon and cream base colours of the Big Bus Company, but with red City Sightseeing logos applied and the large yellow signwriting altered to read 'SIGHTSEEING TOUR OF SAN FRANCISCO'.