Britons can have their citizenship revoked by the Home Secretary.
The Bureau of Investigative Journalism looks into the 16 cases where Theresa May has used that power:
In a case known only as L1, a Sudanese-British man took his four British children on holiday to Sudan, along with his wife, who had limited leave to remain in the UK. Four days after his departure, Theresa May decided to strip him of his citizenship.
With their father excluded from the UK and their mother’s lack of permanent right to remain, the order effectively blocks the children from growing up in Britain. At the time of the order the children were aged between eight and 13 months.
In one case, Theresa May removed a man’s citizenship just before he was seized in Djibouti and rendered to the US. There has already been much reporting around this person, Mahdi Hashi, and there is a group campaigning on his behalf.