Thanks Simon, I'm now back in the UK and it was indeed open.
I found out whilst at the bottom of the staircase, that there's another staircase about half a click up the valley.
That'll have to be for next year as my daughter was already knackered from the walk from the Masieta parking to the first staircase (6.5km, I'm told), of course, us oldies have more stamina than these young'uns.