I should have had the courage of my convictions. The raptor in the last post was, indeed, a Merlin. After everyone had convinced me to look for a reason as to how I could have been so mistaken after being so sure, The Fates intervened. I wish they hadn't. On Saturday the Merlin made an attempt to take a sparrow from the birdtable, overshot, crashed and broke a wing. Although I called the SSPCA and gave her water from a dropper she soon went into shock and died. This morning the ornithologist and vet confirmed that she was a Merlin and that she was far too small to be a female Sparrowhawk even if the markings had not been sufficient identification.
I'd rather have been wrong and that she had lived.