with franchised TOCs, however a number are still in active service with railtour and charter operators. They are also found on almost all mainland UK standard gauge heritage/preserved/tourist lines. Mark 2 The Mark 2 TSO was a direct development of the Mark 1 version, and the early Mark 2 TSOs (Mark 2 and Mark 2a) had an almost identical layout, including the pair of toilets either side of the gangway at one end and the two identical four-bay saloons separated by a just-off-mid-coach transverse vestibule, with further transverse vestibules at the outer end of each saloon. Unlike those in the Mark 1 TSOs, the Mark 2 saloons were not further subdivided. The Mark 2b design saw the centre vestibule abolished, although the mid-coach divider was retained to still give two saloons of four bays each. The space saved by the abolition of the centre vestibule was used to re-locate the toilets, with one now placed at each end, with the entrance vestibules beyond them. This enabled the fitting of wide wrap-round end doors in place of the traditional narrow ones. The basic layout of the Mark 2 TSO remained unaltered from the 2b to the 2f, although finish, materials, seating, and ventilation arrangements changed with each new build. Full details of the various changes are listed in the Mark 2 Development Table in the main Mark 2 article. Usage Mark 2 coaches gradually replaced Mark 1s on crack express services, allowing the older vehicles to cascade down to secondary services and thus enable the steady withdrawal of pre-nationalisation designs. Early Mark 2s were then in turn cascaded as later designs took over top-link workings. Air-conditioned Mark 2s generally worked in express trains on the great main lines, with pressure-ventilated Mark 2s used along with Mark 1 coaches on secondary services. Prior to the introduction of the HSTs, the standard Anglo-Scottish express train on the East Coast Main Line would be formed of a Deltic locomotive and eight air-conditioned Mark 2 coaches. The final mainstay of Mark 2 operation, using Mark 2e and Mark 2f vehicles, were the inter-regional express trains on the West Coast Main Line (hauled by a variety of diesel and electric locomotives), and the Cross Country network, where they were usually hauled by Class 47 locomotives. At the time of the privatisation of British Rail in the mid-1990s, Mark 2 TSOs were operated in sizable numbers by