[buboard]

The vienna diplomatic convention according to which the UK should protect the embassy from intrusion

https://en.wikipedia.org/wiki/Vienna_Convention_on_Diplomati...

[ceejayoz]

The Vienna Convention isn't super clear on what counts as "intrusion", but I suspect it's generally read as physical intrusion - you don't send people in to raid the place. Spying on embassies has a long, storied history.