Alas "merry-go-round" in name only. Although it had the modern HAA hoppers, the actual operation was sad. Part of that time in Edinburgh described above involved the new mainstream colliery in the east of Scotland, Bilston Glen, which was a principal source for Cockenzie power station, it was Scotland's newest (1950s-60s) and largest colliery, but of any "going-round" there was none, the wagons were broken up and tripped through the loading bunker by an NCB shunter, reassembled, coupled Class 20s came down light engine, and took the train a couple of miles, to Millerhill yard, where it was parked up (among the dumped Clayton Class 17s).
Later, further locos came along and took it another couple of miles to the power station, which again was a dead end, no loop. You could actually see the power station from the colliery, but despite all the investment, and a very considerable number of hoppers in the fleet, productivity seemed just like the old days. It wasn't like they achieved in Yorkshire at all. Articles about Longannet power station, much supplied from Ayrshire, seemed just the same. I reckoned at the time you could run Cockenzie entire power station with one single rake of hoppers from its two main collieries.