However, many classes carried 'themed' names, e.g. stars or signs of the zodiac, which aided identification of locomotives to some extent.
Initially standard gauge locomotive numbering was a simple sequential system, starting from 1.
Initially an effort was made to treat the numbering of locomotives bought out of revenue differently from those out of capital, including by re-using old numbers left vacant following withdrawal, using a duplicate number system (unusually, giving the new locomotives an A suffix - other railways tended to apply such notation to the old locomotive being replaced) and, for a few years, using the series 1000 (later 1001) upwards.
In 1875, the sequential system starting at 1 reached 1000 and then jumped to 1116, the other side of the latter range of numbers still carried.
This desirable aim was made more important following the rebuilding of some Duke and Atbara locomotives to Bulldog and City class designs.
Many of these engines were withdrawn after a short period of time, but those that survived in 1946 were subject to another renumbering to rationalise the system further (see below).
The bulk of the locomotives absorbed were renumbered into gaps in broad number ranges according to their wheel arrangement.
In order to tidy up the gaps in this number range, it was decided to renumber the surviving locomotives from each pre-Grouping company together.
The series used were: In 1946/7 a number of locomotives were converted to burn oil, and some were renumbered in the process.
After the end of the broad gauge, names were applied to principal passenger and mixed-traffic standard-gauge locomotives.
However, the classes of locomotives inherited at the Grouping in 1923 continued to be referred to by the classification allocated to them by their original owner.