Earlier quoted context omitted.
Of course, she never had diplomatic immunity - her husband works for the NSA, and was not on the official list of diplomats (those whose credentials are presented and accepted at the Court of St James).
You don't need to be on the official list to acquire diplomatic immunity (that would be an easy way for foreign regimes to deny diplomatic immunity). There are chefs, drivers, etc. who have diplomatic immunity but are not on the official list (because that would unreasonably lengthen it). Additionally, the RAF base her husband was stationed at is legally considered an annex of the US Embassy in London, so arguably sh…
https://grberridge.diplomacy.edu/the-sacoolas-affair-diploma...