Cryptic crossword No 1,823

Good to see you back here, BD, and what a lovely birthday gift! Many happy returns to your son - I hope he will be suitably impressed and delighted. My pick of the clues: 11a, 22a, 26a, 27a (COTD), 2d, 4d and 21d.

Well I trust that your son (5d?) has a good time with this great present! At 13, he must have been infected with the cryptic bug well and truly. There is a high level of sophistication in both the GK and wordplay parsing in many of these clues, such that I found myself challenged in places - presumably the reference to key interests etc will help him. I particularly appreciated 9a, 20a, 25a, 6d & 14d among others. A bit of spoilery discussion in reply.