The 34 members of the class were built by Beyer, Peacock and Company in Manchester, England, for the East African Railways (EAR).

They entered service in 1955–56, and were the largest, heaviest and most powerful steam locomotives to operate on any metre gauge railway in the world.

During normal service, the locomotives were attended to by two regular crews on a 'caboose' basis, one working and one resting in a van with sleeping accommodation, changing over at eight-hour intervals.

The two drivers, Kirpal Singh and Walter Pinto, simply went on holiday when the locomotive went into Nairobi works for scheduled maintenance.

Her cab interior is more akin to a Sikh temple than a locomotive footplate for its boiler face abounds in polished brasswork, embellished with mirrors, clocks, silver buckets and a linoleum floor".