Many Prog Rock bands were Prog Rock by accident, Pink Floyd and Hawkwind fall into this category. However Van der Graaf Generator were definitely Prog Rock on purpose, I am pretty sure Peter Hammill sat up most nights with the Prog Rock Manifesto ticking boxes and making lists.
It is a great album with an absolute golden moment of Prog pomposity, A Plague of Lighthouse Keepers. I just realised this tonight but you have to be pretty posh to be a proper Prog vocalist, I wonder if this is in the Manifesto, even the Durham pit village lad, Bryan Ferry pretended to be Posh.
An aside; I had never before considered the obvious psychological effects of shipwrecks on a lighthouse keeper, thank you Mr Hammill for bring this to light.