Designed for long distance, semi-fast services on the Southern area, the Class 2-HAL was a development of the earlier Class 2-BIL with some changes to the body construction. Although the wooden frame and canvas covered wooden roof was retained, the cab was welded steel. Galvanised steel sheeting sides replaced wooden panels with internal partitions being made of plywood.
Powered by two 275 hp traction motors via a third rail, the 129'5" long two car unit had a top speed of 75mph and weighed 76 long tons. A total of 100 two car sets were built at the Southern Railway Eastleigh Works, using frames from the Lancing Works. The first batch of 76, numbers 2601 - 2676 were built in 1938 for service on the London to Maidstone and Gillingham routes in Kent. This was far more than actually required for the Medway service and was the largest single batch of main line semi fast stock ever built by the Southern Railway.