However, as loads increased, they were replaced by more powerful locomotive types (like the class Z) and relegated to secondary duties.

By 1924, the Gresley A1s started to arrived in large numbers, which displaced the C7s to many of the secondary duties of the D21s, and in particular, York its entire allocation.

Although Edward the Blue Engine, from the Railway Series books and its spin-off television series Thomas the Tank Engine & Friends, is regularly described as bearing "a quite striking similarity" to the Furness Railway "Larger Seagulls".

The Edwardian 4-4-0 type is a fairly common design pattern in British steam locomotives, although at the time of the Seagulls they still had low-set small diameter boilers with tall chimneys.

Edward, in particular, differs in having a cab with dual glazed side windows, a much more characteristic feature of North Eastern railway locomotives, the tapered non-circular spectacle plate windows and also the larger boiler diameter and higher boiler line are distinctively those of the NER R1, by then the LNER D21.