The purebred Hereford cattle breed (distinguished in this report as Hereford (OP) and sometimes known as the Traditional Hereford and Original Population Hereford) has existed in the UK since the early / mid-1800s. It is the forerunner of the North American Derived Hereford (Hereford (NAD)) which has diverged genetically as a result of hybridisation and is largely derived from breeding stock developed in North America following colonisation and continues to the present day. Previous studies have demonstrated that the two groups are different breeds genetically distinct on a scale that indicates introgression of genetic material from one or more additional breeds into the Hereford (NAD). To prevent the risk of outside genetics entering the Hereford (OP) gene pool, we utilised high-density genetic marker testing of Hereford (OP) animals from the UK, Australia and the USA, together with other breed information, to develop a test for distinguishing Hereford (OP) from Hereford (NAD), and to establish the genetic continuity of the Hereford (OP) animals and their distinctiveness from the Hereford (NAD). We demonstrate that this test can correctly identify UK and Australian animals of known/suspected Hereford (NAD) pedigree and those of known Hereford (OP) pedigree. The test can also be used to assist breeders to breed back towards the purebred Hereford (OP), correctly inform new entrants regarding the genetics of the breed and educate the public in general about the purebred Hereford.