Sheep on the M25!

Me and Matt were driving to Egham on Saturday (to the Charity Gig in aid of the NSPCC) and as we were driving along the M25 anti clockwise (approx 80mph) across the other side of the road is a kind of steep embankment, and on the embankment what is the last thing you would expect to see...SHEEP!!, grazing, seemingly without a care in the world while the cars and lorries thundered past emitting all their exhaust fumes and God only knows what else!!
Now as somebody who doesn't eat meat and loves animals I found this a bit difficult to take in.
I recently saw a programme on the BBC about animals and farming (may have been Country File) and there was a farmer explaining about the quality of meat and what makes a difference in the actual taste of the meat and the well being of the animals all the time that they are been farmed.
He pointed out that animals like to be in large fields not overly populated and like green grass to graze on, they like calm surroundings in the country.
So what I want to know is who owns these sheep, and does he know the 1st thing about farming?
Why would anybody (who didn't even know a thing about farming) keep their sheep at the side of the M25 (probably the UK's busiest Motorway) where they are constantly breathing in the fumes, hassled by the noise and totally out of their natural environment, not to mention the planes taking off and landing at Heathrow!!
I'm surprised the vibration from the lorries that go rattling by hasn't caused the sheep to fall over and into the path of a passing lorry!!
Anyway whoever ends up with one of those sheep on their dinner plate this Easter prepare for a mouthful of exhaust fume tasting leg of lamb!!!

I can't find anything on here about an M25 sheep, http://www.nationalsheep.org.uk/education/Chapter_03.pdf