I'd say that wall at 19 has about a 95% probability of being a...

I'd say that wall at 19 has about a 95% probability of being a cap. The term cappers is often used to explain why a stock isn't moving up but why would you place sells for 2.5m, 1m, 8m and 1.5m virtually consecutively 3 pips above the line?

IMHO, because you are happy to accumulate at 16, 17 and 18 and while you sit those sells there sellers are going to come in at 17 or 18 all day. Far enough away to be at no risk of being chomped and perhaps even with the 900,000 as a sacrifice to give you time to pull them if someone else did want a big piece.