The Princess Royal spoke of the “devastating impact” of Equine Grass Sickness, which killed five Highland ponies on the Balmoral estate between June 2017 and May 2018.

The 70-year-old is launching a new fellowship for research into the illness, which almost always results in death for horses. The royal spoke about Equine Grass Sickness on the OnFarm podcast.

Asked if she’d ever encountered the disease, she said: “Yes. More so recently at Balmoral where they’ve had quite a lot of losses sadly.

“And that’s - you know, particularly when you’re breeding Highland Ponies and you lose two really nice colts in one go.

“That’s a pretty devastating impact, as well as the fact that they are working ponies, it’s important to keep those gene pools relevant.”

The manager of the Balmoral Highland Pony Stud, Sylvia Ormiston, appeared on a previous episode of the podcast and revealed that the Queen had visited one of the ill horses before it succumbed to EGS in May 2018.

Ormiston said: “He started to show signs of being sick on the Friday evening. The Queen came to see him on the Saturday... It was enough time that the Queen could come to see him, to actually say goodbye - because there was nothing we could do.”

“It just shows you that no matter who you are, no matter who the animal belongs to, you still can’t save them.”

The new three-year research fellowship is a joint initiative from the The Moredun Foundation (TMF) and The Equine Grass Sickness Fund (EGSF) - both of which Princess Anne is a patron for.

Horse owners and researchers will collaborate in a bid to tackle the deadly disease, which attacks horses’ nervous systems leading to paralysis in their digestive tracts.

Princess Anne said: “I think that for Moredun to launch a Research Fellowship as part of its centenary and to choose to do so on equine grass sickness is pretty significant given their history, background and success in so many areas with livestock and diseases and I am delighted to launch this new Fellowship for equine grass sickness at Moredun.”