1941. A second prototype, 21C2 Union Castle was completed in June and named at Victoria railway station 4 July. Both prototypes were found to be seven tons over the specified weight, and, at the insistence of the Southern Railway Civil Engineer, production of the remainder was halted until steps were taken to remedy this. This was achieved by using thinner steel plates for the frame stretchers and covering the boiler cladding, and enlarging the existing lightening holes in the main frames. The remaining eight locomotives in the batch were delivered between September 1941 and July 1942. A second batch of ten followed, beginning in December 1944 and culminating in June 1945. These were entirely constructed at Eastleigh and equipped with tenders. The Merchant Navy class spawned the design and construction of a lighter version of the same locomotive with consequently increased route availability. These were the West Country and Battle of Britain class Light Pacifics, the first of which entered service in 1945. Just prior to the nationalisation of the railways in 1948, the Southern Railway placed an order for ten more Merchant Navy locomotives, with larger tenders. A shortage of materials meant that delivery was delayed until September 1948, and completed in 1949; the batch never carried Southern Railway numbers. Eastleigh was responsible for the construction of the final batch, which were in the series 35021–35030. Construction was undertaken in-house by Eastleigh works, with the boilers and tenders constructed at Brighton, the frames at Ashford and the rest at Eastleigh. These were equipped with wedge-shaped cab fronts from the outset, and greater use of welding ensured lighter locomotives. The batch was also fitted with the TIA ("Traitement Integral Armand") chemical feed-water equipment used on the Light Pacifics. This precipitated scale-forming constituents in the "hard-water" of southern England into a non-adhesive mud that could be cleared from the locomotive using a manual "blow-down" valve. A delay in the construction of the new larger tenders for the new locomotives meant that some were fitted with the smaller examples intended for use with Light Pacifics that were under construction at the time. Two spare boilers for the class were also constructed at Brighton and Eastleigh during 1950/1. Numbering and naming the locomotives Bulleid adopted a new numbering scheme for all his locomotives based on Continental practice, following his experiences at the French branch of Westinghouse Electric before the First World War, and