@Dunluce - Merlin is a modified Hornby Compound (tender drive). Unfortunately she's been on display so long she no longer runs, but I plan to give her a transplant and DCC her for layout running as soon as I can.
There are some more shots of her, and more models of 85 here: http://irishrailwaymodeller.com/showthread.php/1062-Models-of-Merlin-No-85