Teegate:
I concur with your assessment of some trick photography in the top image above. If you look at it, there an overlay of a second negative covering about the top third of the image. If you blow the image up, you can see the microchips in the glass along the bottom of the overlaid negative. To mask what he did, Capewell laid the second negative down with the emulsion against the base negative to make it appear that the men were on the same plane as the base negative. I presume that Capewell then shot a second unified negative to tie it all together onto a single plate.
That's my $0.02 worth.
Best regards,
Jerseyman