Mark Bullen, a former British police officer with ties to Russia, has been stripped of his UK citizenship on national security grounds as the first UK-born individual to face such action.

Mark Bullen, a 45-year-old former police officer from North London who lived in Russia for 12 years and held Russian citizenship since 2022, was stripped of his British citizenship by Home Secretary Shabana Mahmood due to his longstanding ties to Russia, deemed hostile to the UK. Bullen worked for Hertfordshire Constabulary for 11 years, engaged in multiple exchanges with Russian police, and moved to Russia in 2014. He was questioned under Schedule 3 of the Counterterrorism and Border Security Act 2019 during a 2024 UK airport arrival for suspected hostile state activity. The Home Office noted citizenship deprivation is rare and used against those involved in terrorism or hostile state activities. Bullen has criticized the decision, claiming a lack of due process and requesting a court hearing. This is the first instance of a UK-born citizen losing citizenship over Kremlin links, with previous cases involving non-UK-born individuals.