Devin just posted this wonderful photo of Brian Epstein on Facebook. When I asked him about it, he told me it was taken by David Bailey.
Which led me, as the internet does, to this shot of BE from Bailey's famous 1964 Box of Pinups:
(John himself preferred another shot from the same session.)
You can find many photos from Box of Pinups here. Well worth looking through if you love Swinging London as much as I do.