Dirac Lecture 4 (of 4) - Does ’G’ vary? (Large Numbers Hypothesis)

After these four lectures, Dirac travelled to Australia to deliver more lectures. Unfortunately I don’t know if video recordings of these were made. One lecture included Dirac presenting for the first time, an equation describing the relativistic Boson with spin. I don’t know what became of this work. If anyone knows, can you please post a comment? Much