and West Harrow (towards Uxbridge). The Metropolitan line is unique in operating an express service. "Fast" and "Semi-fast" services (now mostly reserved for peak times) do not stop between Harrow-on-the-Hill and Finchley Road. The "Fast" lines at stations between Moor Park, Harrow and Wembley Park have no platforms. Southbound services go to either Baker Street (4tph) or continue beyond to the line's terminus at Aldgate (12tph). Off-peak trains from Amersham (2tph), Chesham (2tph) and Uxbridge (8tph) generally terminate at Aldgate, with a 4tph service from Watford to Baker Street, however during peak hours trains from all branches go to/from all destinations. Bus Network Adjacent to Harrow-on-the-Hill Underground station is Harrow Bus Station. National Rail The National Rail service at Harrow-on-the-Hill is provided by Chiltern Railways. Services operate between Marylebone station and Aylesbury using the separate Network Rail tracks from London to Harrow and sharing London Underground tracks between Harrow and Amersham. Chiltern Railways started operating in 1996 after the privatisation of British Rail and typically provide two trains per hour between Aylesbury and London via Harrow. Station layout The station building is above ground with the six platforms in a cutting. Two (on the South side) are predominantly used by NR services and the other four by the Metropolitan line; the NR platforms are electrified with the LU system (normal services are operated by diesel trains) and incoming LU trains on some routes can be diverted into them should this be necessary during closures of tracks in the area. The station has two entrances, one on Station Approach (leading to Lowlands Road and Harrow Hill) and one on College Road (for Harrow Bus Station and the main shopping area). During opening hours the Station is popular as a shortcut, removing the longer walk via the bridge at Station Road, as it is possible to walk through the bridge and use the public toilets without passing through the ticket gates. The present main station building replaced older structures at the London end of the platforms (thus leaving Station Road with no station); it consists of a circulating area above the tracks with stairways leading down to all platforms and both street entrances. A pedestrian tunnel once connected all the platforms to the adjacent and now closed Post Office sorting office, whose site was redeveloped. An office block called Avanta House was built in the 1980s on top of the station's College