To the untrained eye, it seems impossible to distinguish between some horses, and even trainers have sometimes confused horses in their care.

Since 1st January 1999, all thoroughbreds born in Britain and Ireland have been "microchipped", leaving no room for error. This entails implanting a microchip half way up the left hand side of the horse's neck at the same time as the foal's markings and blood sample are taken.

Each horse has its own microchip number which will relate to all the information also held on a horse's passport and could, in time, contain additional information on the horse's racing career. A scanner is passed over the horse's neck to read the unique number, so giving a fast and effective way of identifying racehorses. This method will also be used at the sales as well as on the racecourse. The microchip system significantly reduces the scope for cases of mistaken identify, either by accident or by intention. Every horse with a microchip is tested each time it races.

Furthermore at birth, each thoroughbred foal registered in the General Stud Book receives a passport. The passport contains details of the horse's pedigree as well as his colour, and individual markings or whorls (these appear at certain points on the horse's coat where the hair changes direction). It also serves as a vaccination record.

The horse should be accompanied by his passport whenever he travels. The passport allows the horse to enter racecourses throughout Britain, and also to travel abroad, as well as allowing horses that have been registered by another Recognised Turf Authority to compete in this country. It prevents horses from having to undergo lengthy quarantine restrictions and allows them to move freely from one country to another.

On its racecourse debut in this country a horse's passport will be checked by a Veterinary Officer. The vet is not only checking the horse's identity, but also that his vaccinations are up to date. The vet will compare the description in the passport (and microchip where appropriate) with the horse in front of him and check that they tally. If there is any doubt, the horse can be blood tested, as his blood type will have been established when he was initially registered. Passports are checked randomly throughout a horse's racing career and also every time a horse is selected for dope testing.