A former Hertfordshire Constabulary officer has become the first person born in Britain to lose their citizenship due to alleged connections to the Kremlin.
Home Secretary Shabana Mahmood issued the deprivation order to Mark Bullen, 45, in October 2025, just one month into her tenure, stating that revoking his nationality was "conducive to the public good".
The evidence underpinning the decision remains classified, with the Home Office citing national security concerns.
Such measures are typically reserved for individuals accused of terrorism, or involvement in serious organised crime.
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Bullen, who spent more than a decade serving with the Hertfordshire force before relocating to Russia, has publicly denied any wrongdoing and shared the government's letter on social media.
Bullen departed the police force in 2014 and moved to Russia, where he had previously participated in an International Police Association exchange programme that saw him work in the country for a month.
Special Branch officers had questioned his frequent trips to Russia as early as 2013, asking why he was travelling there.
He now resides in St Petersburg, and is employed by Zenit St Petersburg FC - the football club owned by Russian energy giant Gazprom.
Mark Bullen served with Hertfordshire Constabulary prior to his allegations
| ZENITThe company was subjected to UK and US sanctions in January 2025 following Russia's invasion of Ukraine.
The former officer obtained Russian citizenship in 2022, describing it as fulfilling a "lifelong dream."
He has stated that if forced to choose between British and Russian passports, he would select the Russian option "without a second thought".
In November 2024, counterterrorism officers detained Mr Bullen at Luton airport after he arrived on a flight from Turkey to visit friends in the UK.
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Mark Bullen permanently moved to St Petersburg in 2014 | GETTYDuring four hours of questioning under Schedule 3 of the Counterterrorism and Border Security Act 2019, which covers suspected hostile state activity, officers confiscated his electronic devices and asked about his knowledge of the 2018 Salisbury poisonings.
He was subsequently released without arrest.
Bullen has been scathing about his treatment, previously likening British officers to the "Stasi" on X.
Speaking to Russian sports website sports.ru, he said: "It's like East Germany. An undemocratic country. No lawyer, no phone, no water. An ice-cold room."
He added that had someone described such treatment to him during his policing career, he would have deemed it illegal.
Mr Bullen has criticised the secretive nature of the appeals process, stating he contacted the British embassy to verify the deprivation notice was genuine.
He said: "They sent me this document and they said, 'You can appeal the decision, but the trial will be closed and secret. We won't show you the evidence. You won't know what exactly you're accused of'."
He indicated he would contest the ruling if granted legal aid.
The Metropolitan Police confirmed that a man in his forties was stopped at Luton airport on November 12 2024 using counterterrorism powers, with devices seized for examination.
A Home Office spokesman defended the action, stating that citizenship deprivation is "a vital tool used to protect the UK from some of the most dangerous people", and that such decisions are never made lightly.