A gallery from the Silverstone round is now available here -
https://flic.kr/s/aHBqjzNWd8.
Experimenting with the 1.7x teleconverter on the 200-500 zoom gave me a maximum focal length of 850mm on some of the shots although through fence it seems to soften the image a little; aided and abetted by heat haze (yes, at Silverstone in early May !). Dodgy knee meant I stayed largely around Luffield.