 Designed at British Railways ' Derby Works , the new class was constructed at British Railways ' Crewe Works between 1951 and 1954 . The initial order was for 25 locomotives , but such was the demand for the Britannias on the Eastern Region that more were rushed through construction before the teething problems had been ironed out on the prototypes . In total , 55 members of the class were constructed over three batches at Crewe Works , where each was given improvements to improve reliability and efficiency , and to overcome flaws with the original design . 
