After the passenger trains on the main lines on Jutland and Funen had reached a weight of 800 tonnes, the pulling power of the Litra P (II) Atlantic locomotives reached their limits. In view of the good experiences with the Prussian P 8, a new locomotive with the wheel arrangement 4-6-0 was developed with the R (I) and ordered from Borsig.

At 1,866 mm, the driving wheels had a slightly smaller diameter than those of the P (II). The saturated four-cylinder compound engine now received a successor in a simple superheated two-cylinder engine. By relocating the cylinders to the middle of the bogie and driving the first axle, smooth running could be maintained at a high level. The boiler had roughly the same dimensions and was able to produce the same output despite the boiler pressure being reduced from 15 to 12 bars. The narrow and deep firebox was designed for high quality British coal and compensated the smaller grate area with a larger area of the walls.

After the first twelve, a further eight were to be procured by Borsig, but this was not possible due to the First World War. Instead, the Swiss locomotive factory in Winterthur delivered the remaining locomotives. These had a steel firebox, which was replaced with a copper one after the war. The locomotives were eventually retired between 1958 and 1972. An example damaged in an accident was restored and then came to Danmarks Jernbanemuseum in Odense. Unfortunately, it was scrapped in 2018 along with about half of the museum's exhibits.