Slightly unusually for the LNWR, the class received a number series, this being 1901–1940.

The inside cylinders were angled above the outside cylinders and although this could have been solved by cranking the rocking levers, this gave an uneven drive to the valves; valve-setting between both of them had to be a compromise position, ideal for neither, and so gave an uneven power distribution between high and low.

The smokebox was partitioned internally into upper and lower halves, the lower section exhausting through the front chimney and the upper tubes through the rear chimney.

The blastpipes were fed separately, the front chimney from the left cylinders and the rear from the right.

[2] The double chimney was re-fitted to Jubilee, but the production locomotives were built as compounds without it.

[2] The ratio between LP and HP cylinders was 1.69, lower than that considered optimal.

1908 Royal George was withdrawn in January 1923, but the remaining eight were allocated the LMS numbers 5110–5117, in sequence.