really I should have used a lower ISO, maybe 200 would have been better.
However the conditions were quite dark and misty when not shooting into the sun like this so ISO 800 would have kept the shutter-speeds reasonably fast and so not risking any blur.
I'd say on a bright sunny day use ISO 100 or 200 (I hardly ever go below 200), and then on a cloudy day go up to ISO 400 or 800. As long as the shutter speed is as fast as the focal length (remember on a DSLR that you have to multiply the focal length by 1.6 or 1.4 depending on the model), then it should be fine for photographing hand-held.
I hope this helps :-)
Red Deer in the Mist (129) *