If memory serves me well, I'm pretty sure that this originally appeared in the print version of the magazine some years back.
The dynamic of designing, coding and testing had its own lolloping momentum. Smith would draw rooms by hand on large sheets of graph paper, six rooms to a page. (He actually hung on to these first drafts of the Frank Lloyd Wright-inspired mansion right up until the mid ’90s, despite his mother’s dog having urinated on them during the previous decade.) He would then type the relevant numbers into a Tandy TRS-80 Model 4 and any actual coding was done on this machine, before being ‘squirted’, a favourite Smith phrase, on to the target machine: the Sinclair Spectrum.
There's some really interesting stuff to be found here, and it's a must read for any Miner Willy fan.
Thanks go to World of Spectrum forumite Dan, for giving the heads-up on this one.