Consequently, a Keswick resident complained in 1857, "Here we are buried – shut out from the world, as it were – 15 hours from a morning paper while other people know at an instant what happens at the other end of the kingdom"[3][a] However, the prospectus for the company argued, what would make the line profitable was not local traffic to Keswick, but potential two-way mineral traffic between the haematite orefield of West Cumberland and the coke-ovens of South Durham.

[7] The directors were able to make inspection trips to Keswick from either end of the line in May–June 1864;[8] on their trip from Cockermouth they were accompanied by goods waggons,[9] thereafter Keswick was "supplied with coal by rail from the Workington pits"[10] (implying that the Cockermouth-Keswick section of the line was de facto open for mineral traffic).

[16] [b] The CK&PR had agreed with its sponsoring railways that the LNWR was to work passenger and goods traffic on the line (receiving one-third of earnings) whilst the S&D was to work mineral traffic (the S&D to receive 35% of earnings, and the CK&PR to pay for waggons).

The line was laid out by Bouch with the object of the utmost economy; although the bridges were permanent (stone and iron rather than timber trestles).

[29] Unlike the M&CR, the CP&KR had severe gradients (westbound a climb of 1 in 70 between Penrith and Blencow, eastbound 1 in 62+1⁄2 between Threlkeld and Troutbeck)[30]: 210  and therefore higher running costs; a CK&PR chairman claimed that a locomotive could haul on the M&CR a train three times as heavy as it could haul over the CK&PR.

[36][f] Keswick also attracted day trips (works outings, Sunday school treats) from Carlisle and industrial West Cumberland, and was a popular venue for Temperance demonstrations, although much depended on the weather:Soon after the departure from Carlisle the rain commenced to fall in heavy showers, and continued throughout the whole of the day without the slightest perceptible abatement.

Between eleven and twelve o'clock the whole of the excursion trains had arrived, and the streets of Keswick were literally crowded by an immense concourse of people, whose wet and weary appearance indicated the entire absence of enjoyment.

Those local places of interest which have given to Keswick an attractive reputation were unvisited, and the people seemed to wander from the tea rooms to the public-houses during the whole day … If the weather had been propitious, the Demonstration would have proved a marked success, for seldom has such a large number of people accompanied an excursion to Keswick.

As the excursionists returned to the station towards evening, a more reliable estimate could be formed of the number present, which was represented by several thousands.

Beyond a few expressions of sympathy with some loitering excursionists who missed the homeward train, nothing transpired in the shape of an accident to call forth regret save the serious weather, which reminded many of the not altogether groundless proverb that, "it always rains at Keswick"[38]In return for subscribing for £25,000 of CK&PR shares, the LNWR had been granted running rights over the CK&PR in perpetuity.

[40] The LNWR also rebuffed subsequent attempts by the CK&PR to reopen negotiations, and the latter continued to operate as a separate company until the 1923 Grouping, when it was absorbed by the London, Midland and Scottish Railway.

The Keswick to Penrith section followed suit in March 1972, though freight trains continued to run to Flusco and Blencow, at the eastern end of the line, until the following June.

A proposal to demolish the Mosedale Viaduct was cancelled by the British Rail Property Board in 1997 because of the plan to reinstate the line.