Pretty Polly was an LNER A3 Pacific mentioned by the Elderly Brake Van in the annual story, Galloping Sausage. She was named after a female racehorse; the brake van commented that it was a silly name for an engine.
Built in April 1925 as an LNER A1 Pacific, Pretty Polly was rebuilt into an A3 in May 1944. She was first numbered to 2560, renumbered to 61, and finally 60061 under British Railways. Pretty Polly was withdrawn in September 1963 and scrapped soon afterward. She was Gordon, Lemberg and Flying Scotsman's sister and Green Arrow, Mallard, Spencer and the Flying Thistle's cousin.
Pretty Polly first wore the LNER "Apple Green" livery with black and white linings until she was repainted in LNER "Wartime Black" livery during World War II. After the war was over, Pretty Pretty retrieved her original "Apple Green" livery. During the nationalisation of British Railways was in 1948, the engine received an experimental BR "Express Passenger Lined Blue" with black and white linings livery until she was finally repainted in BR "Brunswick Green" with black and orange linings livery in 1952.