Operating Areas: E (East London), EC (City of London)), EN (Enfield), GU (Guildford), HA (Harrow), KT (Kingston upon Thames), N (North London), NW (North West London), SE (South East London), SL (Slough), SW (South West London), TW (Twickenham), W (West London), WC (West Central London), WD (Watford)