Invisible, the Irish-bred black mare with the faint star on her forehead who was the curse of many equine vet students’ practical exams, has died at the age of 30. She spent seven years in retirement at The Horse Trust’s Home of Rest for Horses in Buckinghamshire, England.

Invisible was originally a British Army horse, but she retired from duty in 1984 at age six. At that time she was loaned to the Royal Veterinary College. Invisible had a sino-arterial block, which led to a significant heart problem and dysrhythmia.

“I remember her well,” said Peter Webbon, BVetMed, PhD, DVR, MRCVS, a former senior lecturer in equine medicine and director of the Sefton Equine Referral Hospital at the Royal Veterinary College, now chief executive of the Animal Health Trust. “She was similar to another resident horse with no cardiac abnormality. By swapping their stables during practical examinations, it was possible to identify the students who actually listened to the horse’s heart and those who relied on the grapevine which said that the black mare had a dysrhythmia!”

Invisible was euthanized due to increasing debility and mild ataxia. A post mortem indicated chronic liver disease.

Read more about veterinary teaching horses.