In 1906, the Cape Government Railways placed a single experimental 10th Class steam locomotive with a 4-8-0 Mastodon type wheel arrangement in service on its Eastern System.

The designs were prepared at the Salt River shops of the CGR in Cape Town and represented a further effort on Beatty's part to improve the steaming efficiency of his 8th Class of 1904.

[1][2][3][4] With this locomotive, as with the 9th Class Mikado which had been delivered by the same manufacturer earlier in that same year, Beatty overcame his aversion to boiler centre lines which exceeded twice the Cape gauge track width of 3 feet 6 inches (1,067 millimetres) above the railhead.

[1][2][4] With the 10th Class, on the other hand, he obtained a wide firebox by spreading the grate over the rear coupled wheels, hence the requirement to raise the boiler pitch.

It proved to be very successful in service and was able to handle loads of 280 long tons (284 tonnes) up the steep 1 in 40 (2½%) gradient of the mainline, which began right at the end of the departure platform at East London station at the time.