Despite a branch from this line to Peebles having been put forward, it was struck out of the Bill. Even before the opening of its main line the Caledonian Railway had in 1845 proposed a line from Ayr to Berwick via Douglas, Peebles and Kelso. This proposal was dropped, but it marked the beginning of the fierce competition which eventually developed between the North British and Caledonian Railway companies and so characterised the pattern of Scottish railway history. Later, an Act of 1847 authorised the Caledonian Railway to construct a railway from Symington to Broughton but powers were allowed to lapse.

It is necessary to bear in mind, therefore, in gaining an appreciation of railway developments around Peebles that the North British regarded the counties of Peebles, Selkirk, Roxburgh and Berwick as its own inviolable territory. Peebles thus became one of the notable frontiers between the two largest and most powerful railway companies in Scotland.

In 1845 an independent group was formed to promote a double line of railway between Edinburgh and Peebles by way of Penicuik. Capital was assessed at £250,000 and the preamble to the Bill went through Parliament in 1846. However, this coincided with a general proliferation of schemes, many of them hare-brained, the period becoming generally known as the 'Railway Mania'. Inevitably the bubble burst and many proposals including the Peebles one were abandoned.

There the matter rested until 1851 when some Peebles residents, frustrated by the unsatisfactory horse-drawn transport serving the town, and, noting the rise in prosperity which the coming of the railway had brought elsewhere, got together to reconsider a rail link with Edinburgh.

These well-intentioned men were William Chambers of Glenormiston; Walter Thorburn, the banker; and John Bathgate, writer in Peebles. The railway was to be a local line founded on the most economical principles of construction and operation. The services of Mr (later Sir) Thomas Bouch were secured to conduct a survey of the suggested route which was from Eskbank on the Edinburgh and Hawick line by way of Bonnyrigg, Hawthornden and Leadburn, just south of which the summit at 930 feet above sea-level would be reached, and thereafter down Eddleston Water to Peebles, a distance of 18.75