Chris, as Mark says, and I don't want to turn this into a WAA thread, the two waters do have double figure tench in them even today. The third which I'm not going to name other than say Mark has got it right in one of his posts, does also have doubles that get caught in it. But because of idiosyncrasies of the water, you only get about 3 weeks to have a crack at catching one. Or as Graham Marsden has called it many time in the past in articles "Duffers Fortnight!" Then they are gone until the next year.
A quick story from the 80s on one of the Chesh/Shrops meres. I fished this mere for over 20 years in total for it bream and tench. It was around the middle of the decade 85-6 and I had many 10s if not several 100 of tench from it, but the best I ever caught was 6 12. and the best I knew coming out of it was a massive 7 03. Then one Saturday evening a guy and his lad fish the other bank caught two tench within minutes of each other that I could see were big fish even at 100 yards distance. The guy then appears in my swim asking me have I any scales. Asking why, he says we've got two tench mine 8 12 and my lad's 9 08 on my scales. good grief them are big fish, in fact, never heard of any bigger than 7 03. I’ll come round with you to see these monsters. I’ll be honest, I thought he’d mis weighed them. Off we trot and he say you weigh them just in case I got it wrong. So I did and recorded the same weights he had. I congratulated him and his son for getting the best pair of fish that I knew of out of the mere.
As I knew probably 95% of the lads that fished the mere, they were stunned that it had thrown up tench of that size. Thankfully, the guy and his son sent a picture of the two fish into Angling Times and from the photos those who knew the mere, knew the swim and could see they were very big fish indeed.
The moral of the story being we might think we know how big the fish are in a water, but really we don't!