Yeah I have been once, and that was enough. Really awful experience. (Went about a decade ago) with my friend, and her daughter (her DD was 14 at the time,) and some of the behaviour from some people was repugnant. Aggressive, shouty, confrontational, people arguing, and shouting at one another and anyone who looked their way. Whole place stunk of cannabis, people were setting fire to things, people were fighting, the works....
Scared all 3 of us, and it took us nearly an hour to get away. The closest tube stations were closed and no-one was allowed in, so we had to walk an hour to find one that was open. (Would be half an hour walk normally, but it was so crowded, and people were packed in like sardine, so we struggled to move at some points.)
At one point we were around 40 people deep in every direction and there was no escape as we were all packed so tightly in. My friend had a panic attack, and said 'gotta get out gotta get out gotta get out!' 😖Several girls around her said 'where the fuck you think you're gonna go, there's 1000s of people packed in together. Get over yourself'
We managed to wriggle through eventually, and got to a side alley, (about 2 minutes walk down it,) but when we got to the other side, it was just as bad. I approached a policeman and asked if he could help as my friend was having a panic attack, and he kindly allowed us to go down a route that had been closed off, and we managed to be free of the huge, tight crowd(s.) Even so, a bit further up the road it was still very busy, but not packed in so we couldn't move.
Still had to walk for an hour from that point to get to an open tube station. Never EVER would I go to the Notting Hill Carnival again. Worst experience ever. I have been to loads of concerts, festivals, carnivals, (including several 'pride' ones,) and outside music parties with 10s of 1000s of people around, and NONE of them were as bad as the Notting Hill Carnival. Nowhere near.
It really needs binning off...