The ingredients quantities for this mayo were probably perfect, but the method just didn't work for me unfortunately! Pouring all of the oil on top of the egg rather than having to drizzle it in slowly turned out too good to be true this time.
If this happens to anyone else, I was able to remedy it by letting the watery mixture sit for 10mins, as this allowed much of the oil to separate out into a top layer. I then poured off this top layer, and added one more egg yolk to what was left. Blitzed until that thickened, then slowly drizzled in the oil layer while blitzing. Turned out lovely in the end!