I’m not fully convinced of my identification, but then I took the photo thinking it was a Chiffchaff. However, no eye-stripe and that streaked crest is not right for a warbler. Worse, it was over-exposed (at ISO8000, 1/1250s) so my corrections may have spoiled the balance of light to dark.
Prospect Park, Reading, UK
Canon R5 MkII + RF200-800
The Merlin app is what gave me the lead, though then looked it up in the WILDGuide Britain’s Bird book.