Matching VIN and Engine Numbers

Is there anywhere where I can check if a Defender carries its original engine. My TD5 is supposed to have had a replacement engine but I think it might be the original (and therefore older). I called Land Rover who said I should contact my dealer as they didn't keep this info (?????). I called a dealer and spoke to the Customer Service lass who whilst painting her nails and chatting with her office mate said they didn't have the data and couldn't help.
Any help/advice from members would be appreciated.

Thanks

Darryl

dvla should have a record of not only the current engine number, but any changes that have occured