Blimey. All that advice and only a day to get your telephotographic gubbins together and haul it up onto the roof of Selfridges along with a friend to help you get the focus right. Am I correct that he is recommending focussing without a filter as long as the “magnification is very high”? Also looking directly at the Sun through the finder tube to line the camera up. Health and Safety clearly wasn’t much of a thing in 1912. I doubt if they had high railings around the roof either.
British Astronomical Association
Supporting amateur astronomers since 1890