The Caterham line is a railway branch line running from Caterham in Surrey to Purley in South London. It operates as a commuter service to London. The line was opened by local promoters as the Caterham Railway in 1856 primarily to convey firestone from quarries south of Caterham. There was intense rivalry and suspicion between the two main line railway companies at Purley, the London, Brighton and South Coast Railway (LBSCR) and the South Eastern Railway (SER), and this led to both of them obstructing successful operation of the Caterham Railway. In any case the local population was sparse and agricultural in character, and the Caterham Railway was loss-making. It was acquired by the SER in 1859, but it was not until the latter years of the nineteenth century that residential development made the commercial situation of the line more buoyant. The line was doubled and a programme of station and infrastructure improvements was completed by 1900. The line was electrified in 1928. After many years allied to the South Eastern Division of British Railways, the line is now operated by the Southern train operating company; a half-hourly service to London Bridge is operated. History The main line to Redhill and Brighton By an Act of Parliament of 1846 the London, Brighton and South Coast Railway was formed. It controlled the line from London Bridge to Brighton, but by Act of Parliament, it shared the line from London Bridge to Redhill with the South Eastern Railway, which turned east at Redhill and ran to Tonbridge and beyond. Caterham Railway proposed Local promoters put forward what became the Caterham Railway. The primary objective was the conveyance of firestone, an important refractory mineral, from quarries above Caterham; the population of the town was only 487 in 1851, so that passenger business was not expected to be dominant. The promoters of this line had applied to the LBSCR for a connection at Godstone Road, the contemporary name for Purley. At the time there was a territorial agreement in force, made in 1848 between the LBSCR and the SER, that neither company would construct or encourage the construction of a new line in the other company's area of influence. The London to Redhill railway line was taken to be the demarcation line. Accordingly the LBSCR asked the SER for their view on the proposal. The SER evidently feared that the LBSCR would use the