One of the Home Secretary’s more startling powers is to take people’s British citizenship away where they acquired it by fraud or it is “conducive to the public good”. In the latter case, losing citizenship often amounts to exile in the interests of national security: the tactic is to wait until the person is abroad before making the deprivation order. Under the Nationality and Borders Bill, the person need not be told about the order at all.

The Home Office tells us that this power is used “sparingly”. Between 2010 and 2018, “only around 19 people a year were deprived of their citizenship on ‘conducive to the public good’ grounds”. Whether that is rare or routine depends on your point of view, but the average conceals an upward trend in recent years (insofar as figures are available). This week alone, Free Movement covered two separate appeals against citizenship deprivation — one of which was argued by our latest podcast guest, Alasdair MacKenzie of Doughty Street Chambers.

I spoke to Alasdair about the law on citizenship deprivation, his experience fighting cases in the SIAC national security court — “like wrestling with a shadow” — and the role of judges in policing one of the state’s most draconian powers.