Stills have pointed out that they have a talk in the Gallery space upstairs between 6 pm and 7 pm. Have a look at their website for details. If you arrive at Stills before 7 pm you will need to wait until the talk is over to gain access downstairs. Camera Club will go ahead as normal downstairs after the talk finishes.
So, choices are: to go the talk and then on to Camera Club, or time your arrival for after 7 pm.