“If the Russians or the Chinese recruit a CIA case officer or FBI agent… maybe $1 million per year, in that range,” said a former Western intelligence professional who spoke on condition of anonymity. “We would actually pay less for someone on their side.”

An Afghanistan asset might only earn £200 to $2,000 a month for low-level or economic intelligence, while a senior Chinese Ministry of State Security officer or a Russian ex-KGB or Federal Security Service officer could command a minimum of $200,000 a year.