The Claud Hamilton, particularly in its original GER blue livery, is widely considered one of the most elegant locomotive designs of the pre-grouping era.

In his 1955 history of the Great Eastern Railway, Cecil J. Allen devotes a whole chapter to the class and noted that Of all the locomotive designs that emerged from Stratford Works during the reign of James Holden, the one destined to achieve the greatest fame, beyond question, was his Claud Hamilton type 4-4-0, of which the pioneer example, No.

Ellis was informed by Russell that during the process of designing the locomotive "Mr Holden, by then a valetudinarian was making a long recuperative stay in Egypt.

[2] Class pioneer No 1900 Claud Hamilton featuring red lining and connecting rods, copper chimney cap and GER coat of arms was much admired when it was exhibited at the 1900 Paris Exposition.

The oil burnt was a waste product of the GER's gasworks that produced Pintsch gas for lighting its carriages.

The GER had previously been fined for discharging this waste product into the River Lea, and the railway was thus able to fuel its oil-burning locomotives at little extra cost.

Holden had always intended that his oil-burning system would allow engines so fitted to be easily converted to burn coal if required, and all the S46s and D56s had been switched to coal-burning by the end of 1911.

[1] Allen reports that Claud Hamiltons in their original state were capable of taking around 350 tons from Liverpool Street to North Walsham in under the booked time.

Most earlier members of the class were substantially modified by Hill or during the tenure of Sir Nigel Gresley as CME of the LNER from 1923.

The appearance was altered when a larger boiler and Belpaire firebox was fitted, meaning a change in the cab window shape as well.