Thanks all for your welcome, comments, tips and patience. I’ve found another photo, in “The Art of Hornby”, p76. Without the people you can clearly see the mainline disappearing into a ‘tunnel’ as per New Lad’s diagrams, meaning the layout is probably a diorama - although it could theoretically curve under the track above. I tried V4 of the track planning book and couldn’t find anything. Perhaps this pic might trigger a thought for others involved, eg Railway Modeller staff. Still chuckling about the ‘man with pipe’! Thanks, Andrew