Willow Warbler? and Muntjac deer

Hello all.

I took advantage of a quiet spell at work yesterday morning, to take the camera for a walk.

As the heading says - the highlights were the deer and what I believe to be a Willow warbler. I did ponder for ages over whether this bird was a Chiffchaff or the Warbler , but in the end I am leaning towards the latter. My basis for this is the song description, in the end. 

Any comments and corrections most welcome.

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Stay safe everyone.

Tony