Jersey Tiger Moth Euplagia quadripunctaria

Jersey Tiger moth
Jersey Tiger moth red underwing
The Jersey Tiger, active by day and by night, is found in the Channel Islands (hence the name Jersey); some are also present in Devon, Dorset and Somerset and a recent, growing population exists in London - these in northwest London - spreading into the Home Counties currently.
Jersey Tiger moth
Jersey Tiger moth
Jersey Tiger moth yellow underwing
P.S. That was nearly a decade ago; today (2020) they are more common in southern UK. They are also native to most of Europe through to Central Asia.
Jersey Tiger moth
Jersey Tiger moth
Jersey Tiger moth yellow underwing
Usually the underwings are red with black spots but sometimes they have a yellow background. Wingspan 42-52mm; UK flight time Jul-Sep.
Jersey Tiger moth Above from SE London by Bob Clark. As usual, he gets the subject to pose on his hand.
Jersey Tiger moth Above from Surrey by Martin Starnes, who also manages to get the subject to pose on his hand.
Always difficult to hold the camera in the other hand, steady enough to take the one-handed shot.
Jersey Tiger moth
Jersey Tiger moth
The two Jersey Tigers above are from Emily Tutton, taken near the athletic (previously Olympic) stadium in Stratford, East London. She says the moth was "friendly and beautiful" and also manages to get a pose on her hand. She adds "I thought you might like the pictures as your site helped me to identify it!" (Always glad when the site serves its purpose.)
Jersey Tiger moth
Jersey Tiger moth red underwing
The moths above were photographed by Martin Starnes in his Surrey garden. He says: "I have now photographed thirty plus species in the house or garden in the last few weeks, most identified thanks to your website" - it's always good to know that the site is helpful.
Jersey Tiger moth underside
Jersey Tiger moth underside
Jersey Tiger moth
The undersides of the two above were on my NW London kitchen window (2017 and 2019 respectively), and the topside on the garden wall (2020).