Anyone know what a ‘caution horse’ is?

CAUTION: I have met race horses, cart horses, carriage dray and many more different breeds – I have never ever met a “Caution” horse.

Even though I have spent most of my eighty years in Sussex most weekends I see several horse boxes carrying “Caution” horses - it is plainly written on the front and back. Others state race horses, cart horses, etc.

So if anyone can describe one to me a photograph would be nice, thank you.

P.S. I do love horses but they can be dangerous!

David Mills

Orchard Close