It took me a bit longer than usual as I had spelled 3 down incorrectly. I was struggling with 11 & 12 across for about 15 minutes until I noticed, then it all became clear. Worst clue for me was:
19A Skin change deceives a city in Africa (8)
as the use of "deceives" shunted me on to a siding.
I also agree with Caravaggio that the use of "Island nearly" in 21A was very tenuous.