Today, more than 100 GWR broad gauge freight locomotives, which originally belonged to different classes, are called the Caesar class. They all had the 0-6-0 wheel arrangement and were designed by Daniel Gooch and built in Swindon. In contrast to their predecessors, they did not have a haystack firebox, but one with a round top.

Using the possibilities of the broad gauge, they were significantly more powerful than other locomotives with this wheel arrangement. Due to the gentle curves of the broad-gauge tracks, the wheelbase could be made very long in order to obtain sufficient running smoothness despite the lack of carrying axles. At five feet in diameter, the wheels were smaller than the boiler diameter.

The actual Caesar class consisted of eight saddle tank locomotives built in 1851 and 1852. Their service life ended between 1871 and 1880. A restructuring of the class names in 1865 resulted in the Pyracmon, Ariadne and Caliph class tender locomotives being included in the Caesar class.

The seven Pyracmon class locomotives were based on the Premier class, which were the first locomotives built in Swindon and were to be phased out between 1871 and 1873. The Ariadne and Caliph classes were also referred to as “Gooch Standard Goods” and were delivered in seven lots between 1852 and 1863.

Most locomotives were named after gods or well-known figures from ancient Greece, but some were named after British rivers or given other names altogether. This resulted in 102 locomotives that were retired between 1871 and 1883. An exception was the “Europa”, which was extensively rebuilt in 1869 and remained in service until 1892, when traffic on the broad gauge was discontinued.