Mainline steam trains in Great Britain
The most famous steam locomotive operating on the British main line is the 1923 built "Flying Scotsman". After being taken into public ownership in 2004, following a decade long refit it returned to mainline service in 2016. The fastest steam locomotive ever built, the 1938 built "Mallard", was also certified for main line operation briefly in the 1980s.
SJ D
When the passenger locomotives were given more powerful motors, they were designated Dk. They had a maximum speed of 100 km/h. This is the last series of locomotives that was built new, all later types have been rebuilt, except the one-off experimental subtype Dr. The last Dk loco was built in 1943 and concluded eighteen years of D production. When the production of Da-locos started in 1953, the Dks were rebuilt to the same engine, and received the designation Du. The last use of Dk was in 1975. In total 117 have had the Dk designation, of which 73 were built as Dk.