The 71-year-old, who holds both UK and US passports, is the richest Welshman who has ever lived, external, with a wealth built on investments in companies like Yahoo and Google that made him billions during the dot-com boom of the early 2000s.
In a memoir called Ausländer – the German word for foreigner or outsider – Sir Michael charts his family’s treatment under the Nazis.
His paternal grandparents, Max and Minnie Moritz, were among swathes of relatives killed during the Holocaust.
Using public archives he found that two of his relatives, his great-uncle Oskar Moritz and his cousin Mira Marx, were photographed by the Gestapo as they were forced onto buses that transported them to their deaths.
Sir Michael’s parents had escaped Germany and settled in Cardiff, where he attended the now-closed Howardian High School in Penylan.
He said the sense of being an outsider had accompanied him since childhood and recalled opening the phone directory as a teenager and scanning the “M” section, hoping his family would not be the only entry under “Moritz”.
“There was no shortage of Evans’ and Thomas’, but we were the only Moritz.
“And to me, that was as if – in the margin, in big black capital letters – it said Jew.”