Cryptic crossword No 1,451

Thanks Natrix. More than one cuppa needed alongside this one, although I’m a bit distracted at present. A bit tougher than I remember previous ones of yours being, but in a good way mostly. I enjoyed 11a, 12a, 16a, 18a, 20a, 26a, 27a (COTD), 2d, 4d, 5d mostly with the satisfying mental ‘clunk’ after just the right amount of time. A few queries or quibbles in reply, spoilers…