Oh, the wretched!
I was on the straight and narrow and had a sell order that was ‘good till day end’ but it triggered at 12:00 auction (which I wasn't aware of by the way,
only knew about morning/afternoon auctions).
So I was thinking ‘glitch’. Logged out, logged back in, profit was still there.
Happy days – short lived.
I contacted them, seems they didn’t know about the midday auction glitch, should have just shut it.