With the work carried out at Swindon Works, the first to be converted was 5275 (lot 266), which returned to traffic numbered 7200 in August 1934. An official photograph of the prototype was taken on 27 July 1934 at the usual site outside 'A Shop' for engine pictures. Nos. 5276–94 were similarly rebuilt between August and November 1934, becoming 7201–19, and nos. 7220–39 were rebuilt from 5255–74 between August 1935 and February 1936; with both batches, the rebuilding was not in numerical order, but the new numbers were in the same sequence as the old. Nos. 7240–53, rebuilt August 1937–December 1939, were selected at random from locomotives numbered in the 4200 series.