Together the three railways would connect central Scotland to Perth, Forfar and Aberdeen, and with the Caledonian and its allies they would link to London as well.

In due course, the Caledonian was to find that these payments were unaffordable, and it was able to escape them by demonstrating that they were ultra vires, that is, that their company had no powers to make such commitments.

Quite apart from this dubious outcome, relations between the companies were not always amicable, and in fact the Scottish Central Railway was robustly independent for some years.

It had been built as a stone block sleeper line on the local track gauge of 5 ft 6in (1,676 mm) and the Aberdeen Railway seems not to have fully understood the financial implications of converting this to a modern double track main line on the standard gauge.

)[3] The Aberdeen company ran into financial difficulties of its own, running out of cash in 1848 after building from Guthrie to Dubton, with branches to Brechin and Montrose.

Both of these were stone block sleeper single lines built to another local track gauge, this time 4 ft 6.5in (1,384 mm).

In 1846 the D&AR had obtained powers to build an extension at Arbroath to link with the A&FR, and to convert its own track gauge to standard; this was in use from 1848.

The station was increasingly becoming a traffic hub, and by Act of Parliament it was transferred to the control of a Joint Committee, representing all the users.

GNoSR traffic to the south, principally live cattle, was mostly forwarded by coastal shipping and through passengers simply had to walk between the two stations.

had stipulated the construction of a line through the Denburn Valley to link with then former Aberdeen Railway, the GNoSR made it plain that it was content with the status quo, although local people and northern farmers were not.

The scheme was highly attractive to the SNER as it would bring it much traffic that was denied to it; equally the GNoSR was dismayed at the possibility of losing income diverted away from it.

It was to cross the Deeside Railway at Peterculter and make two short branches connecting to it there, which would give the line access to Aberdeen in addition.

At this time Aberdeen was heavily built up, and the GNoSR quickly developed a scheme that would run in a wide loop round the western margin of the city, entering the SNER Guild Street station from the south.

Nonetheless it would have required significant demolitions of residential buildings, and, costing £125,000 for less than three miles (5 km) of route, it attracted considerable hostility locally; its circuitous alignment brought it the mocking epithet "Circumbendibus".

[citation needed] In parliamentary committee the objections were so significant that the promoters agreed that a previous proposal, the Denburn Valley Railway should be substituted, the capital of the GNoSR scheme and of the SNJR being combined for the purpose, amounting to £200,000.

The Denburn Valley line would run directly from Kittybrewster on the GNoSR to a junction with the SNER near Guild Street; a new central Joint Station (to be managed by a joint committee) would be built, and the portion of line north and south of the station would be allocated respectively to the GNoSR and the SNER.

In 1878 the NBR bridged the Firth of Tay at Dundee, giving it direct access from Edinburgh and Fife to the north shore of the Firth, and Parliament ordered that the Dundee and Arbroath Railway be transferred to joint ownership: jointly between the Caledonian and the NBR.

This took effect from 1 February 1880, and gave the NBR an independent route from Edinburgh to Kinnaber, and running powers from there to Aberdeen.

When the railways were nationalised in 1948 this state of affairs continued and the pattern of passenger and goods trains remained relatively unaffected by the new common ownership.

The railway network is substantially unchanged from that time; domestic Scottish passenger services are operated by ScotRail.