Thanks Gareth, that answers my question. I asked for a couple of reasons, firstly "The Book of the Warships" mentions 870 being sent to Derby for experiments with gas turbines, (and I'd love to know more about that) but was returned as unsuitable because of collision damage, so I wondered if 832 was the replacement. Secondly I read on another forum that 832 had a minor overhaul, including a bogie change I think, at Laira before being sent to Derby, so I thought that might indicate it was to be used as motive power. Anyway, apparently not, so at least I know why I haven't seen any pictures of 832 on RTC trains.
Thanks again
Mike