OK, that's embarrassing. After looking for ages, as soon as I posted I found it ... of course.
I must have dragged it all the way down at some stage, and because the arrow was not there to 'restore' it, didn't even think of it being slid away and dived into settings. After a tinker I just discovered that when you drag it all the way down, the icon to restore it also disappears. Which is great for a cleaner look, tricky if you don't realise it's actually still there.