@Charlie Simmomds My apologies for not reading the second half of your answer and repeating what you had already said 
I have three answers next - all equally possible, I think. Great grey owl, Ural owl or northern hawk owl, they all nest so far north that they have to hunt during the day in summer as well as at night.
I have three answers next - all equally possible, I think. Great grey owl, Ural owl or northern hawk owl, they all nest so far north that they have to hunt during the day in summer as well as at night.