When I first bought Chertsey, I remember someone telling me that about twenty boats had Petter PD2 engines. I'm not sure now whether that was in some sense right, has be overtaken by time and events, or most likely, was always an overestimate. Racking my brains at Braunston, I could think of only five: Chertsey, of course, plus Cassopaeia, Alton, Aldgate and Darley. Lancing did have one, but has recently been changed - in many, more obvious, ways as well as the engine.
So I did what anyone would do, and posted the question on CanalWorld in the hope that the walking encyclopaedia that is Pete Harrison would be unable to resist responding. And it transpires that while there are perhaps a dozen or so boats around with PD2s, only eight of these are ones that had the engines fitted by British Waterways in the late fifties and early sixties (the ones I'd missed were Comet, Stratford and Greenock - Comet I should have remembered because I have seen it, when we went to see Ian Kemp and his legendary stock of PD2 spares to replace a missing bit of tinware).
So, I went on to ask, how many boats did BW fit these engines in in the first place - and the answer surprised me: sixty eight. Far more than I had expected. These seem to have been the boats that passed into BW's Southern carrying fleet - those in the North were more likely to get air cooled Listers.
So out of 68 (possibly in fact more), eight remain. I love my PD2 despite its numerous leaks and recent tendency to smoke, and am very proud to be part of such an exclusive - but with such good provenance - club.