Harry's books have been out of print for a long time, and the websites that his son Colin created have gone the way of their free hosting providers.

However, I have recently obtained permission and blessings from Harry's family to curate and update his works, and the first fruits of this can be found at the new Glasgow's Secret Geometry website, which includes an interactive map of all the sites and alignments in his Forgotten Footsteps and Glasgow's Secret Geometry, plus some sites and alignments from my own work, and a couple of Alfred Watkins' leys of Roman forts on the Antonine Wall, as mentioned in The Old Straight Track.

It's a work in progress with more to come, but I hope you find it useful.