Of German Swiss parentage, he played leading roles on stage and in films in Argentina. He went to Hollywood in the 1950s and was typically cast as a European womanizer. His Hollywood films include The Flame and the Flesh (1954) with Lana Turner and Pier Angeli, Valley of the Kings, (1954), with Robert Taylor and Eleanor Parker, Magic Fire (1955) in which he played Franz Liszt, opposite Yvonne De Carlo, Rita Gam and Valentina Cortese.
He moved to Europe and appeared in a large number of German films. He was chiefly known to English speakers for his appearance as Carlos Varela in the 1963 ITC Entertainment series The Sentimental Agent. In the late 1960s, Thompson left acting to become a writer and TV producer.
His first success on the European book market was The assassination of Winston Churchill (1969), a refutation of allegations by David Irving (Accident. The Death of General Sikorski, 1967) and the German playwright Rolf Hochhuth (Soldiers, premièred in the UK in 1968, London) that war time premier Winston Churchill had a part in the death of Polish General Władysław Sikorski, who perished in an air plane crash at Gibraltar on July 4, 1943, allegedly due to sabotage.
Although references to him recorded in the diaries of Noel Coward suggest that he was bisexual, Thompson married German-born actress Lilli Palmer shortly after her divorce from Rex Harrison. Thompson remained married to Palmer until her death in 1986.
Thompson committed suicide by a gunshot to his head in 1990.
(as written in Wikipedia - free online reference service)