I just wrote a scene where Portiais sitting on the roof deducing that Brian Dawes has just come from dinner and a movie with his girlfriend Annie Coleson, and I need some details.
Firstly, yes, cinemas existed in 1931 in London.
At first I thought the Gate Theatre (originally a studio near Covent Garden, opened I. 1925) would suffice, but it was for plays, not movies. I’ll hold onto that one for some later use.
I think the Nottinghill Coronet would be a reasonable choice.. located at Pembridge Road and Holland Park ave in Notting Hill Gate in London, it’s close enough to Baker street to make it the ‘local’ theatre.
This is from the Wikipedia article:
In 1916, films were shown at the theatre for the first time, as part of variety programmes mixing live and filmed performance.
In 1923, it became a cinema full time, and capacity was reduced from 1,143 to 1,010 seats, but it retained, as it still does, its original theatre interior, consisting of stalls and two upper tiers (a dress circle and a gallery). However, the boxes at each side of the auditorium, next to the stage, were removed in 1931. The stage has been blocked off, and the cinema screen is placed within the proscenium arch. The projection equipment is housed in the former dress circle bar.
In 1931, the cinema became part of Gaumont British Cinemas, and it was at this time that the theatre boxes were removed.
That leaves the dinner, somewhere Brian could have oysters with a special aoli Portia would recognize. This area I think has been known as Nottinghill for some time, and seems to have a rich restaurant district. I think this spot works.