The specific mission these folks are on is basically one that's normally executed by a Coast Guard, of which Iraq hasn't one yet. Shortly before the incident, that group had finished an interdiction on an India-flagged tanker (the subject of the photo from yesterday). This is what they have been doing for years. The usual set of Targets Of Interest are: smuggling, weapons proliferation, illegal oil transfers, money laundering, all the usual suspects.
I want to re-emphasize: I do not know, and I don't think we'll ever know for sure, what exactly happened or who was 'in the right' -- is Iran confused about where this took place? Maybe. Did the patrol group see an opportunity to test the Iranian Navy? Maybe. Did the Iranian Navy notice that HMS Cornwall was enough out of position to allow them to score a point? Maybe.
But these patrols are UN sanctioned and have been going on for a long time and have included Canadian ships as well. It is specifically that those waters are disputed that it's important to patrol them: it's a perfect place for smuggling operations.
They most specifically are not:
> Either spying, or trying to provoke an incident, no?
/jordan