There's only officially a PVR of one, for the 19, other than bank holiday weekend when they should have another two out on the E1. Previous bank holidays this year when open tops were advertised, they didn't hesitate to sub conventional vehicles and indeed currently 17645 appears to be the only one that's operational, and a couple of days saw Service 19 run with standard closed top vehicles (including one day when 17645 was on the Es!).

So - even if 17239/40 and 17643 remain off the road, doubt very much that they will draft in any further open toppers for one weekend. I think the current offerings are only in existence as they have the Tridents sat doing nothing. Suspect it may well be the last year SNE have open tops at all, sadly.