Sadly tonight, as I checked out the District Dave forum, I discovered that Dave had died today and many of the forum regulars were posting tributes.
I have mentioned this site more than once. It is a goldmine of information about the Tube, many of the contributors being drivers, station assistants, signalmen, line controllers and the like. The site will go on, of course, but without its presiding spirit. What a great contribution to the Web he made.