Here's an account which raises the issues fairly.
http://www.bbc.co.uk/news/uk-48645280
Obviously I don't have access to intelligence. It may be the near certainty of the British government has some authority.
But I think the statement that only Iran makes sense, makes no sense. Lots of folks operate over there and have devious purposes. Some share American and/or UK interests. Some wish to draw Western militaries into existing local conflicts. Some wish to cause trouble for trouble's sake. If the UK foreign secretary lacks the requisite jurisdictional cynicism, he will make misjudgements.