It's virtually a deliberate trap, isn't it ? The only possible approach is from under the bridge, and this sign is there:-
https://maps.app.goo.gl/SG3acMnGEHUPeRrm6
Essentially, the only place you can get to is the car park but this is blocked-off with bollards. So you have to turn right and go up the ramp to Waterloo Bridge Road: -
https://maps.app.goo.gl/2RNgCPkenTdqayym8
then where you go only God can help you !
So why were you driving along Upper Ground ? Following an out-of-date satnav maybe ?
I approached from Waterloo Bridge down to Upper Ground to find parking, as there used to be P&D bays on there. I turned right onto Upper Ground, drove under the bridge, saw that Upper Ground eastbound was now blocked off with the no motor vehicles sign.
I then reversed into the National Theatre car park approach to turn around. The thought did not enter my head that I would have driven through a one way no motor vehicle sign. I completed the three point turn, completely missed the signs and drove back the way I came.
The last time I drove on Upper Ground, it was an unrestricted, two-way road with a fair few P&D bays. I personally think the signage is inadequate. The sign showing the road layout under the bridge doesn't actually show the sign I went through, as it is in the opposing direction to that sign, so the only way to catch it is to spot the signs as you are turning right out of National Theatre.
