Original: Langston , Keith : Made in Crewe : 150 Years of Engineering Excellence , p. 64 ISBN 0-9552868-0-8 A gap now existed in the roster for locomotives with 8P power classification , of which the demand was high for the efficient operation of heavy expresses on the West Coast Main Line between London Euston and Scotland .
Simplified: Langston , Keith : Made in Crewe : 150 Years of Engineering Excellence ( Mortons Media : Horncastle , 2006 ) , ISBN 0955286808