 The Britannia Class was based on several previous LMS locomotive designs , and also significantly influenced by the Bulleid SR Pacifics , notably in the boiler and rear truck design , incorporating the best practices in locomotive technology as regards labour @-@ saving and lowering maintenance costs ; various weight @-@ saving measures also increased the route availability of a Pacific @-@ type locomotive on the British Railways network . The Britannias received a positive reception from their crews , with those regularly operating the locomotives giving them favourable reports as regards performance . However , trials in some areas of the British Railway network returned negative feedback , primarily due to indifferent operation of the locomotive , with its effects on adhering to timetables . 
