The Southdown Company was formed in 1915, by a merger of three firms, formerly bitter competitors. The Brighton, Hove and Preston United Omnibus Company had been a horse-bus proprietor since 1884, in the area suggested by the title, and had introduced motorbuses successfully in 1903. Worthing Motor Services was an offshoot of a former bankrupted steam-bus firm, Sussex Motor Road Car Co, centred on Worthing; it was on the services between Brighton and Worthing that much of the competition focussed. Thirdly, the London & South Coast Haulage Company entered the passenger field, only in 1914, after an unsuccessful haulage career; it ran services from Brighton to Hurstpierpoint and Lewes. The merger of the three firms was forced by the difficult operating conditions of the First World War. The new Southdown Company, based in Brighton, inherited 38 buses of various types.
Between the two World Wars, Southdown expanded by taking over 69 smaller firms, many of whom contributed to the coaching side of the business. A particularly interesting acquisition was Tramocar of Worthing, who operated a fleet of Shelvoke & Drewry vehicles, in 1938. However, for new vehicles Southdown standardised on Leyland's, and this emphasis remained visible despite deliveries of numerous non-standard types and the acquisition in 1969, of the mainly Bristol fleet of Brighton, Hove & District Omnibus Co. Ltd.
After the second world War, a co-ordination agreement was concluded with Portsmouth Corporation Transport, in 1946. In 1961, the company joined the Brighton area co-ordination scheme, which had earlier involved Brighton Corporation and the B.H.& D. company; previously protective fares had been applied, in Brighton, against Southdown services. The B.H.& D. company had grown out of the Brighton area fleet of Thomas Tilling Ltd, of London; most of these operations had been acquired, in 1916, from the Brighton, Hove & Preston company, which one year before, had sold its out of town buses and services to Southdown. Thomas Tilling Ltd lost its extensive London business to the London Passenger Transport Board in 1933, and consequently in 1935, the Brighton business was reconstituted as a separate company. It passed to State ownership in 1948, with the rest of the Tilling bus interests, unlike Southdown, which was part of the BET group; the two companies remained distinct, until 1969, when both were taken over by the National Bus Company. In the same year N.B.C. merged them and B.H.& D. buses began to receive Southdown green livery; a vestige of the old B.H.& D. company remained for a few years, with the use of joint "Southdown - B.H.& D." fleetnames on some buses.
The Southdown livery, formerly apple green and cream, became N.B.C. standard leaf green. The Head Office was at Freshfield Road, Brighton, and the central engineering works at Portslade. Vehicles were garaged at Bognor Regis, Brighton (Edward Street), Brighton (Freshfield Road), Brighton (Whitehawk Road), Chichester, Crowborough, Eastbourne, Emsworth, Hailsham, Hayling Island, Haywards Heath, Hilsea, Horsham, Hove, Lewes, Moulsecoomb, Petersfield, Portsmouth, Seaford, Uckfield and Worthing.; there were also several "dormitories", including the parking ground at Leigh Park, Havant, shared with Portsmouth Corporation.
TO be continued...