The design that became the standard Southern Railway brake van was introduced in 1928 and were known by staff as 'Pillboxes' . The design was soon modified to diagram 1579 and detailed changes were made in later batches, notably the use of distinctive '2+2' planking . No. 103 was built by the Southern Railway at Lancing in 1941 to for the Ministry of Supply for Army use with the further modification of external brake cylinders mounted on an veranda end.Of the first batch 16 went to the middle east and the 103 is one of the four to remain in the UK . A further 20 were built, two of which served on Colonel Stephens' Shropshire and Mongomeryshire Railway and came into BR ownership.

No 103 seems to have been always based at the Longmoor Military Railway and carried several Army numbers ,latterly AD49022 It was purchased by the K&ESR in 1969 and in 1974/75 it was restored and equipped for use as a breakdown van. It received a further heavy overhaul in 1982 and ran for some years in SR freight brown with SR number 56459. Re-entered service in July 2006 following a very heavy overhaul and repainted in BR livery carrying the number of one of its ex Shropshire and Montgomeryshire brethren ( M 360327).