Douglas is twin Scottish mixed-traffic engine.
Douglas was built by John F. McIntosh at the St. Rollox Railway Works in Springburn, Glasgow, Scotland and worked on the Caledonian Railway in Scotland, a large network that extended along the country's east coast as well as the central and south-western regions. Despite being limited to Caledonian metals, they appeared to have a familiarity with other railways, as they were familiar with the locomotives and livery of the Highland Railway.
Giving long and stalwart service, Douglas eventually became 57647 on the Scottish Region of British Railways. In 1959 Sir Topham Hatt needed a goods engine and by his request, BR transferred 57646 to Sodor.
To Sir Tophan Hatt's surprise though, two engines arrived. Donald's twin Douglas could not stand to be separated from his brother, and was smart enough to realise he would eventually be scrapped if he stayed in Scotland. Neither engine could be told apart: both claimed to have forgotten their numbers, and indeed their numberplates had "slyly slipped off" during the journey from Scotland, forcing Hatt to keep both until he could determine which engine was freeloading on his hospitality. It was later revealed that this piece of skulduggery had been planned not only by the two engines, but also by their drivers and firemen, who were all related.
The Fat Controller was unaware of Douglas' motive and threatened the two that whichever engine he found out to be the truant would be sent home. Both engines resolved to give outstanding service so that Hatt would want to keep both of them. This plan quickly went to pieces, however, after Douglas accidentally shunted Thomas' special coach, full of passengers, into a siding at Tidmouth, causing a great deal of fury for the passengers. Things were more complicated when Donald crashed into a signalbox at Tidmouth and Douglas destroyed the Spiteful Brakevan.
Despite all this grief, the twin's professionalism, competency, strong work ethic, and personable natures had begun to win them support, particularly when they demonstrated an aptitude for snowplough work that they had learned in Scotland. After rescuing Henry from just such a snowy ordeal, the other engines came over to Donald and Douglas' side which ultimately led to the engines of Sodor taking industrial action. After a suggestion by Edward, and being pushed into it by Gordon, Percy was presented to the Fat Controller as a deputation, arguing the twins' case on their behalf and pleading that, if sent away, they would be scrapped. Hatt's reaction to this was mixed - though he understood the engines' feelings he did not approve or appreciate them trying to interfere with his decision-making. However, Percy's statement and the twins' excellent performance was enough for Hatt to take pity on the twins and keep both. He demonstrated this intent with an offer of a fresh coat of paint for both engines, and by their request they were painted NWR blue.
Since then, the twins have, by all accounts, "transformed" goods traffic on the main line. Such is their versatility that they regularly see service on the Arlesburgh and Brendam Branch Lines, as well as duties as station-pilots at Tidmouth. A turntable has been provided for them at Arlesburgh, although briefly decommissioned after Oliver was pushed into it by some trucks.
Such a demanding work-load has begun to tax them, however, and in 1993 the Fat Controller borrowed a navy saddletank named Wilbert from the Dean Forest Railway to deputize for them on the Arlesburgh branch, with the intention of at some point obtaining another engine of Wilbert's class to permanently fill that role.