While US authorities cannot enter Iran's diplomatic premises, they could prevent Mr Amiri leaving.

BBC: Stills from footage of "Mr Amiri"

And other attacks that we have seen have been focused on the interface between Western interests here, whether it's the oil companies, whether it's Western tourists or the diplomatic premises here.

NPR: Embassy Attack Marks Rise Of Al-Qaida In Yemen

It now has a permanent president of the European Council (representing national governments) and it is creating its own diplomatic service, which will need high-security premises.

ECONOMIST: Much stroppiness lies ahead in the EU budget negotiations