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 in the author's 1996 book Aether Science Papers which is of record in the author's website www.aspden.org.