Atomic Systems

I've been wondering about what locomotives were used on south wales valleys coal traffic from the transition from steam to diesel. the 0-6-2s are well known for the area but what locomotives replaced them? Being a WR area, were hydraulics ever used? Or were they too light for heavy freightwork? I know 37s became almost universal but did they directly replace steam locomotives?

Seems that class 14 "Teddy Bears" were used for a time

http://www.railblue.com/pages/In%20Dept ... 2014's.htm

Steve

Thanks, a little surprising, i suppose they're pretty much the nearest to the previous tank engines that did it before, and being downhill it's braking ability of the train over the need for power or speed.