Those are Percherons, as the article says, albeit with a bit of flannel about Shires. That's 'Percherons' as in 'Mortagne au Perche', and in the miseheard Spandau Ballet lyric, 'I don't need this Percheron'.
The horses in my video are Belgian Ardennes, working on PAWS Restoration. The speech is a layman's guide to what that means in practice, activated by proximity. It must freak the deer out a bit.