Triffids on the march! I have noted in several other entries that Echium pininana is naturalising in parts of London (for example in St. James's Park, see entry dated 14 June 2019). Strange to say some of the best specimens I've come across are in next door's garden. 

 It's a long way from the natural habitat of E. pininana in the Canary Islands but they self seed readily and grow vigorously despite the garden being rather shady. They are called Giant Echiums/Tree Echiums with good reason; in previous years they have grown as tall as the first floor windows.