In an entertaining article about meeting FH in 1930, Julian Maclaren-Ross mentions a "Mr Kalnay" who was apparently a Hungarian writer and publisher who had also written under the name Jim McKay.
I had been unable to identify this mysterious figure but one of my correspondents pointed out that Jack Kahane might fit the bill, Kahane being also a writer and publisher and certainly someone who might have been at a dinner party given by FH in 1930, as it was in that year that he bought the rights to My Life and Loves.
This identification also throws an interesting light on FH's description on the same occasion of My Life and Loves as "filth". FH might have been endeavouring to make his wares more attractive to Kahane, or possibly, if Kahane had already paid for them, teasing him.