There is the smell of singed hair in the air at Kexwith: it must be horn burning time.
Once their horns have grown large enough, Swaledale sheep (and other horned breeds) are horn burned to help identify which flock they belong to. This involves pressing a heated brand with unique initials against the outside of the horn: the sheep don't even feel it, as it is "dead" horn.
The smell of burning hair is because horn is compressed keratin, which is the same material as hair, and horse hooves (which is why a farrier always smells like burned hair). Each time Ray puts the brand back in the gas powered mini forge which keeps them hot, small particles of horn instantly ignite, causing little billowing flames.
It is a job that requires quite a lot of effort: Swaledale sheep are surprisingly strong for their small, wiry frame, and keeping a firm grip on the sheep to ensure it doesn't struggle while the brand is pressed against the horn is hard work. As Ray says, "If you don't get a hold of them, they'll get a hold of you."
Read more about lambing at Kexwith here.