Juvenile Goshawk at March Farmers

I was very lucky to see just my third Goshawk in the Peterborough area on Saturday, while scanning the massively flooded March Farmers, Cambs. I saw a female Marsh Harrier powering over the flooded washes seemingly in pursuit of something, accompanied by some excited Carrion Crows. At first I thought she was chasing a male Marsh Harrier off her territory, but there was something odd about its shape: it was roughly same size as the female Marsh Harrier, but heavy and with much shorter wings and a very long tail. It almost looked like the raptor equivalent of a Pheasant. Also, how come the harrier couldn't catch up with this bird in front? Then I noticed it was heavily streaked on its breast, and the penny dropped... Here are record shots as it flew over the Nene Way powering south (the harrier and crows had given up by now). I reckon it could be a female, as it was very large (and absolutely nothing like a Sparrowhawk, folks). But I may be wrong.