So far as I can see on GSV the sign says "Resident permit holders only" together with a "B" identifier.
There are no times stated, at least not in the bay the OP identified. I take that to mean that only "B" permit holders can park there at any time. So the bay is 24 x 365. Unfortunately Westminster don't permit Blue Badge holders to park in their resident permit bays, during their hours of operation. And that is common in London and not peculiar to Westminster, Kensington and Chelsea etc. Some boroughs will allow BB holders and others don't. However, but not applicable to this case, there is no yellow line exemption for BB holders in Westminster, K&C, CoL etc as stated in the BB guide.