Official (rather terse) headnote:
The deportation of a former Malaysian national and former BOC is liable to be deemed unlawful where relevant Government Policies relating to inter-state arrangements with Malaysia have not been taken into account or given effect.
I’ve got some sympathy for the Home Office on this one. The President asserts that it is “incoherent” to describe a British Overseas Citizen as “a British national albeit that he does not have a right of abode” (paragraph 27). That seems to me actually to be an accurate description: a British national but not a British citizen, the two being distinct for various slightly arcane reasons of colonial withdrawal.
Other than that, though, it rather looks like the Home Office had rather made a hash of things.