Yes, there was a first book, called "Think Box". I have it, if you want to borrow it :-) But I'm afraid the HCDS thing was in it, and not in Second Thinks (I checked last night), so if you've only seen Second then you won't have seen the bit I'm thinking of.

I agree that HCDS has a nice swing to it, and I did idly wonder at one point whether that was something to do with it - but was foiled by the fact that I couldn't quite tell whether I only thought it had a nice swing because I was so used to using it as my default order.