writes:

My source (Keene's book on Nimzo, written in the days when
Keene was a good writer, but still doubtless fallible) gives
the above tournament and one just called "London" 18-30 July.
It does not give a sponsor's name.

The crosstable generally agrees with your comments
above, but says that he beat Tartakower and drew with
Vidmar.

My mistake, sorry! I misread the crosstable in Keene's book about
the "Empire Club" event, the one in October. Nimzovich tied for
first with Tartakower. He lost to Marshall and Winter, drew with
Vidmar and Reti, defeated seven other people, including Tartakower.