The Caledonian Railway had to operate many express trains with two 4-4-0 locomotives and also needed a helper locomotive at Beattock Summit. To improve this, McIntosh developed a 4-6-0 in 1903. Initially these were just two locomotives, numbers 49 and 50, which were based on the Dunalastair and had inside cylinders. Although these became the flagship of the CR, their performance was not outstanding and there were no sufficiently long turntables.
After longer turntables were built, McIntosh had five improved locomotives built, numbers 903 to 907. The 903 was the only one in the new series to be given the name “Cardean” and thus gave rise to the nickname of the class. All of them received a superheater in 1911, but due to the reduced boiler pressure they hardly had any noticeable increase in output.
However, since this reduced coal consumption, all of them were taken over by the LMS in 1923. There they were soon eclipsed by the LMS Compound and Royal Scot. They were retired between 1927 and 1933, with the exception of the 907, which was written off in 1915 after Britain's worst rail disaster.