I wrote here [my Portuguese blog on secret war in Portugal, 1939-1945] about Peter Ustinov's father, Ivan [Joan, alias "Klop"] biography written by Peter Day.
Compared with what I knew from other sources, the author goes further claiming that, received in Lisbon, in February 1944, by Desmond ("Derry") Bristow [Mi6] "Klop" [Mi5 codenamed U-35] was sent here to meet not some German circles conspiring to assassinate Adolph Hitler, but specifically Otto John [Luftahansa lawyer in Madrid that was later exfiltrated to Gibraltar due to the combined efforts of PVDE's - Portuguese secret police - and Rita Winsor [Mi6 in Lisbon, posing as typist in the British Embassy].
Moreover he emphasizes that Ustinov was acting under the authority of Harold Russel "Kim" Philby [Section V of Mi6, Portuguese desk] a long term soviet mle in the British intelligence community. That I knew already from two different sources: Rufina, Philby's wife after he defeated to the Soviet Union, after the book she wrote Kim Philby Private Life and Genrikh Borovik, a Tass journalist wth KGB connections The Philby Files, published the first in 1999 the second 1994.
The mission of "Klop" served the strategic interests of URSS concerning the non-support of these who intended to kill Hitler. The coup failed and Hitler's life was saved. And war contnued...