Markov originally worked as a novelist, screenwriter and playwright in his native country, the People's Republic of Bulgaria, until his defection in 1968. After relocating to London, he worked as a broadcaster and journalist for the BBC World Service, the US-funded Radio Free Europe and West Germany's Deutsche Welle. Markov used such forums to conduct a campaign of sarcastic criticism against the incumbent Bulgarian regime, which, according to his wife at the time he died, eventually became "vitriolic" and included "really smearing mud on the people in the inner circles."