Herdwicks ... ah yes, our native Lake District sheep. Famous for having their own ‘heaf’ or bit of the fells which they stick to without hedges or walls: they’re ‘heafed’ or ‘hefted’. ‘Gorgeous animals - and very tasty - but their wool is indeed like Brillo pads! Make great hard-wearing carpets though. So yes, they’re hard, and hardy. But I don’t know any song about them. Jake Thackeray has a great one about Swaledales though...