Hello Elin,
Congratulations, you've cracked it - I'm sure now of the event and its location! I have 2 photographs of the event, with Cyril Ratcliffe and his wireless equipment set up at the base of a major monument/statue which is set in a large square. Unfortunately, the heavy smog/fog makes the location very difficult to identify from the photos and we assumed incorrectly that it was City Square. However, having your information and then looking via Leodis at photos of the Queen Victoria monument (which was located in Victoria Square from 1905-1937), I am convinced that Cyril & his equipment was set up there on 23 April 1924, with his back to Leeds Town Hall and the statue of Sir Robert Peel to his right side.
Thank you very much indeed for your most helpful research.
AL