Oliver is the number 11 of the NWR
Oliver is based on the Great Western Railway's 14XX Class of 0-4-2 Tank Engines. Designed by Charles Collet, 75 locomotives were constructed at the GWR's Works at Swindon between 1932 and 1936. Originally Classified as the 4800 Class, they were designed to work with the GWR's Autocoaches, a specialized coach designed for push/pull trains. The Reclassification into 14XX came in 1946, following the GWR's Decision to convert 12 members of the GWR's 2800 Class to oil firing, which themselves were reclassified as 4800's, hence the reclassification. The class was withdrawn between 1956 and 1965, with 4 members surviving into preservation.
Oliver Specifically is based on engine #1436, who, sadly, was not among the 4 14XX's that survived into preservation.