The LNER Gresley A4 is one of the most iconic express locomotives in Great Britain, with its streamlined casing a classic symbol of the attitude towards speed and design in the 1930s, which saw increased competition to the railways from road and air travel. The LNER Board knew they had to make travel between the major cities faster, comfortable and more reliable.

Nigel Gresley, the LNER's Chief Mechanical Officer, travelled on the Fliegende Hamburger diesel locomotive in Germany and was impressed by its streamlining. However, he realized it was only efficient at high speeds. Gresley was certain that a modified A3 Pacific, with streamlining, could haul greater loads than other locomotives at the same speed or faster and a series of trials were conducted to confirm the A3's suitability.

With the trials successfully completed, the LNER Board gave Gresley the go-ahead to create the Silver Jubilee streamlined trains, the first of the new streamlined A4s. The streamlining of the A4s' steam circuit, higher boiler pressure and extension of the firebox to create a combustion chamber, made them more efficient than the A3. As they consumed less coal and water, especially later on when they were also fitted with a Kylchap double chimney. This improved their free steaming capabilities further. 

Their streamlined design not only made them capable of high speeds but created an updraught of smoke, obscuring the driver's vision, a major problem on the new Class A4 engines. The story goes that during wind tunnel testing, after several unsuccessful efforts to get the smoke to lift clear, a thumbprint was inadvertently left on the clay model just behind the chimney. This succeeded in clearing the smoke and was incorporated into the final design.

Union of South Africa was one of five LNER A4 locomotives designated to haul the Coronation train, such locomotives can be identified from the British Empire derived names. The locomotive was introduced as 4488 on the 29th June 1937, with the name Osprey originally allocated to the locomotive but not assigned. 

The locomotive would be withdrawn from the BR service in June 1966 and has gone on to be preserved. During preservation, the locomotive would carry its originally assigned Osprey name for political reasons. The tender connected to 60009 Union of South Africa in preservation is that originally connected to LNER 10000, the W1 Hush Hush, one of the only manifestations of the experimental engines remaining.

Hornby Dublo A4 models feature a diecast body, just as their original Hornby Dublo counterparts would have seen. This is coupled with enchanted decoration which when paired with the diecast of the boiler provides a realistic finish to the body. The models contain a 5 pole motor with flywheel and are DCC ready with an 8 pin socket. These models will also contain a detail bag containing etched nameplates and headboards, allowing the model to be displayed as it would have appeared at the Great Gathering.