The quality of the original design was such that No. A866 was put on display at the British Empire Exhibition at Wembley from May to November 1925, and no class-wide modifications were made until 1934. This was when the SECR and Woolwich batches began to receive new domes and front footsteps during overhauls and general repairs. These were the same design as those used on Nos. 1400–1414, and were intended to standardise components between the batches. The SECR and Woolwich batches also received smoke deflectors to prevent drifting smoke from obscuring the driver's vision ahead. The U1 chimneys replaced the standard N class type on the earlier locomotives, which, along with the removal of the piston tail rods on the earlier batches, created a truly standardised appearance.