Cryptic crossword No 189

A second attempt, trying to build on the feedback from my previous. Themes are hard!

Thanks Newington, pretty tough but I enjoyed it. I like the creative way the theme was integrated, especially 13a. Favourite clues were 3d, 12a, 11d and 14d. I don't think the accident in 20a is a common device but it made me chuckle!