Here's a close up of what I'm looking at from the 1118.07 low which I have labelled as wave (4) of [C] of a zig zag/second zig zag (see the after the close update):
SPX 1 min - from 1118.07 low:
The main reason I'm thinking that wave (5) is forming an ending diagonal is because of that wave from 1122.57 to 1128.75. At the moment, it doesn't look or count like an impulse, whereas the other two waves I've highlighted can be counted as 5 waves (indeed, I did count the first one as 5 waves in my update at 17:41 BST).
Even if I assume that wave (4) was a triangle ending at 1122.57, its still difficult to see an impulse at the moment.
Now, I've seen this before where price action can turn something that looks like that wave into an impulse, so I can't rule out the possibility that it will develop a more impulsive structure with further price movements.
For the time being, as mentioned in the 21:25 BST update, the invalidation point for the ending diagonal will occur if wave 5 exceeds 6.18 points. Until then or until the waves look more like an impulse, I'll assume the ending diagonal is playing out.