Went to Wentlooge Level’s yesterday – very dry but while walking on sea wall this gull flew over – first i thought just BH gull but size didn’t match, then the grey face hood – ask UK Gull 4 beginners as i thought Glaucous – no black tips on wings and mentioned and confirm by 4 sofar on and gaining lot of like and thumps up – somebody suggest bit rare
Glamorgan Bird Club 
Wow, well spotted! Lucky (or skilful) that you got a nice photo. ‘A bit rare’? – it was only admitted to British list in 2016! https://bou.org.uk/azorean-yellow-legged-gull/ I’ve found a very detailed open access paper on ID of this subspecies . The head pattern of yours looks good. https://www.researchgate.net/publication/346442220_Identification_of_Azores_Gull
Thanks – Luck it came right me as saying goes right time and out there