All I could find are these two paragraphs, taken from Doug's 1981 book Racers- the inside story of Williams Grand Prix engineering.
Frank took on an ex- March design engineer named John Clarke. He was a quiet, bespectacled, rather introverted engineer who had been responsible for the 1972 March Formula Two cars, which were very good indeed....
Towards the end of season, in his search for engineering aid which he could persuade himself to trust, Frank called in (Gian Paolo) Dellara to advise on the cars. He decided that the rear suspension geometry could be improved, advised John Clarke, and Frank insisted Clarke make the modifications. This led to a split: " Right or wrong I decided I had had a basinful of engineers learning about Formula One at my expense, and when John objected to my calling in more experienced men over his head, like (Ron) Tauranac or Dallara, we parted not on the best of terms..."