Summer Flower at St. James Park, London The photo was taken on August 24, 2019 at St. James Park, London, UK. If you know what this flower is, please let me know. *** As one friend pointed out, this flower is very likely to be Verbena bonariensis. They are also called purpletop vervain, clustertop vervain, Argentinian vervain, tall verbena, or pretty verbena. See below for this flower. Verbena bonariensis - Wikipedia This is about the..