Kestrel or Merlin?

I'm inclined to believe this is a kestrel - and I've photographed a kestrel in this area previously, but I was slightly ambivalent when Google ID went straight to Merlin. Merlin ID went to Kestrel with Merlin as the second alternative.

I have photographed a Merlin before, in a different area, which was much more easy to ID as the colour of the back/wings was very grey and the white streak above the eye much more pronounced.

can anybody with more experience confirm?