Southdown Motor Services can trace its history back to a pair of steam buses which operated between Pulborough and Worthing. However the company itself was formed in 1915 abandoning plans to call itself South Coast Motor Services (a similar name had been registered by a Folkestone operator). British Electric Traction took an early interest in the company as did Thomas Tilling. The original registered office was in Middle Street, Brighton and in 1916, a garage was built in Freshfield Road. The operating area of the company was bounded by Eastbourne, Portsmouth and the Sussex border.