robp - so it did, I missed that, must have scan read it. Would have saved me some time :-/
mickledore - I have done quite a bit of bike racing and still do in fact so I am aware of the speeds involved, and fast moving is relative of course and a bunch going across the field of view at 25 mph sometimes in poor light I would consider fast.
Of course my field of experience is in landscape and wildlife so I cannot claim to know what I am talking about when it comes to sport.
However I can assure you that many photographers on the World Tour circuit use flash and since my original post I have done a little more research and I found this interesting video and he often uses flash during the race
View: https://vimeo.com/39822833
Also cylists are often looking down (ish) with shadows from helmet etc so a little fill flash is desireable in my opinion.
On the matter of annoying riders by using flash I can assure you this is not my experience. I have used it both on TT's and RR situations and asked for opinions and not a single rider found it an issue. I used it trackside at the velodrome the other night and the coach was happy for me to use it and so were the riders.
Incidentally if you watched Alex Dowsett breaking the hour record you will have noticed that the photographer(s) were using flash on almost every lap, Im sure if it was a distraction he would not have allowed that. Also no doubt you watch the TdF and World Tour races? You will see that the moto photographers often use on-camera flash.
For the record the above is not argumentative, merely my observations. I have a lot to learn.