Cryptic crossword No 3,470

903 - Benign Efforts - also available at https://ibendr.github.io/xwd/bendr/index.html along with over 500 more

Very clever deployment of theme as usual, a history lesson for sure. And lots of neat clueing. My faves include: 9a (brilliantly ghastly surface),22a,27a,29a and 7d (COTD),18d,23d,26d