on the South West Mainline near in 1929. This proved that with the right components, Urie's original design could perform well. Despite the successful use of modified N15 components to rebuild Nos. E448–E457, the mechanically similar "Scotch Arthurs" proved disappointing when put into service from May 1925. The performance of those allocated to the Eastern section was indifferent, and failed to improve upon the double-headed ex-SECR 4-4-0s they were to replace. Reports of poor steaming and hot driving and tender wheel axleboxes were common from crewmen and shed fitters. After investigation, the problems were attributed to poor workmanship during construction as the North British Locomotive Company underquoted production costs to gain the contract. Defects were found in boiler construction across the batch, and necessitated six replacement boilers, re-riveting, re-fitting of tubes and replacement of firebox stays. The hot driving wheel axleboxes were caused by the main frames being out of alignment. A 1926 report suggested that all affected locomotives should be taken to Eastleigh for repair. Once repaired, the "Scotch Arthurs" proved as capable as the rest of the class in service. "Scotch Arthurs" Nos. E763–E772 received new tenders between 1928 and 1930 in a series of tender exchanges with the Lord Nelson and LSWR S15 classes. This ensured that they could exchange their Urie bogie tenders with the Ashford design for use on the shorter Eastern section routes. Whilst useful for the roster clerks at Battersea shed, any transfer to the Western section was hampered because of their shorter range. By 1937, all had reverted to the Urie bogie tenders, though Nos. E768–E772 were attached to new Maunsell flush-sided tenders with brake vacuum reservoirs fitted behind the coal space. These were again swapped with Maunsell LSWR-style bogie tenders fitted to the Lord Nelson class. The second batch of "Eastleigh Arthurs" displaced the ex-K class tanks and ex-LBSCR H2 "Atlantic" 4-4-2 locomotives on the and routes respectively. They were well liked by crews and used on this part of the network until the arrival of electrification. No. E782 Sir Brian was used on the former Great Northern main line for performance trials against the SECR K and K1 class tanks following a railway accident at Sevenoaks, Kent in 1927. The tests were supervised by the London and North Eastern Railway's CME, Sir Nigel Gresley, who commented that the class was unstable at high speeds. The instability was caused by motion