We've been here before. Don't underestimate Iran's enthusiasm for trouble-making.
"They should not be under any doubt at all about how seriously we regard this act which was unjustified and wrong."
Those words could easily be placed into the mouth of foreign secretary David Miliband in response to the arrest of five British civilian sailors in the Gulf.
It's not yet clear whether they strayed into Iranian territorial waters or not. Either way, their detention on suspicion of "evil" intentions deserves the condemnation above.
But these words weren't spoken in 2009. They were uttered by Tony Blair, 32 months ago, about another diplomatic crisis with prickly Iran.
Then Revolutionary Guards soldiers detained 15 British service personnel for straying into Iranian waters in the Shatt-al-Arab waterway which divides Iraq and Iran.
Iran's purpose, then, was as clear as day. It sought to embarrass and humiliate Britain. Deep unease was only underlined further when the soldiers were returned, wearing freshly-tailored suits, after several weeks of discomfort.
Fast forward two years, and the Iranian response to British activities during the disputed presidential elections showed there was still no love lost between the two countries.
As Iran publicly accused Britain of fomenting unrest in the aftermath of Mahmoud Ahmadinejad's unconvincing victory, the Foreign Office was again faced with a kind of provocation it could do without.
Supreme Leader Ali Khamenei said Britain was acting deliberately. Diplomats were expelled in tit-for-tat measures. A British embassy staffer was detained and held for weeks.
In London the mood was one of frustration. British officials were determined to avoid losing face to Tehran. But they could not be seen to act too harshly, either, to avoid fuelling Iran's self-fulfilling fears about an external threat.
Exactly the same problems face Britain's diplomats now. Only after the short-term headache of persuading a deeply hostile nation to give back Britain's civilians will the diplomats be able to turn, once again, to the reasons for their antagonism.
Dealing with the immediate crisis requires a finessing of studied anger and practical negotiations. This is what the Foreign Office does best. But it's a measure of the Iranian problem's depth that it hasn't been able to defuse the tensions which triggered this outrage in the first place.