Hornby R3980 BR, Class W1 'Hush Hush' Streamlined, 4-6-4, 60700 - Era 5Having completed nearly 90,000 miles of test running since new, Sir Nigel Gresley's W1 4 6 4HP 10000 entered Darlington Works on 21 August 1935 for what was anticipated to be a major overhaul and modification. During this period Gresley decided that it was time to rebuild 10000 as a three cylinder locomotive with a conventional firetube boiler and 10000 was moved to Doncaster Works on 13 October 1936, the first drawing for the modification being