And now finished, with some use of CrosswordSolver.
LoI: 17a. (Should have got it sooner from def and 2 crossers: all I could think of was "salad".) (Though the 15d crosser was very late too)
An entertaining puzzle: not sure I found all the thematics. Brockwell said there were 16. I think I found 13, possibly two more: what did I miss?
I found:
Across: 5, 10 ?(t.. s.. beetle?), 11, 12, 13, 16, 17, 19 (well, there's what seems to be a quote connecting them, never heard it before), 23, 24? (T.. t.. sounds vaguely familiar in one order or the other), 26, 28
Down: 3, 9, 24
There could have been a Lily.