The A1 Class, which numbered 49 locomotives in total, has usually been accredited to AH Peppercorn of the LNER, but in reality their construction was authorized when Thompson was still the Chief Mechanical Engineer at Doncaster. The first 16 were authorized for construction at Doncaster in October 1945, followed by an additional 23 in 1946, built at Darlington. The remainder of the class was built at Doncaster in 1949. Five of the class, Nos. 60153-60157, were fitted with Tomken roller bearings. This was to achieve greater mileages between heavy repairs and proved highly successful. Normal locos averaged 100,000 miles, whilst the roller bearing locos averaged 118,000 miles. The locos were initially un-named when built. They later took old names from the Class A4s when some were re-named, others were named after previous Chief Mechanical Engineers and constituent companies of the LNER. The last of the class was withdrawn in 1966 and all 49 locomotives were scrapped with none surviving into preservation. 'Tornado' 60163 was built by the A1 Steam Locomotive Trust not as a replica, but as an evolution of the LNER Class A1 locomotives. It was the first such locomotive built in the UK since 'Evening Star', the last steam locomotive built in 1960.