Yeah, it's easy, just be a wellborn member of British aristocracy.
The result is curious indeed. It appears that Kim Philby's father, St John Philby, was a senior civil servant, but not an aristocrat. He was what was called in those days an "Arabist" and had converted to Islam.
He does seem, however, to have passed onto his son a love of intrigue...
His official role was to protect British interests with the House of Saud, being Ibn Sauds right hand man. Instead he was also on the payroll of Standard Oil, and sold out to the Americans. This alone should have been a warning to the establishment
Dora's parents: https://www.geni.com/people/Dora-Philby/6000000013566932381