The following is a paper by H. Aspden published in Physics Essays, v. 2, pp. 173-179 (1989).
Abstract: This summary account of the author's theory of gravitation enables the reader to calculate G in terms of the electron charge-mass ratio. A classical approach to electrodynamics adapted to relate to lepton interactions yields the unifying link with the gravitational interaction. The tau-lepton is found to be a primary 'graviton' mediator. The theory has a common foundation with methods of deriving the fine structure constant and the proton-electron mass ratio already published in summary form.
The full text of this paper may also be seen in PDF format as Paper No. 10 [1989b] in the Appendix to the author's 1996 book: Aether Science Papers.