My two earlier posts have caused quite a stir, so here are some further observations.

Sadly, but perhaps predictably, both the British and Iranian governments are now acting like idiots.

Tony Blair has let it be known that he is “utterly confident” that the British personnel were in Iraqi waters. He has of course never been known for his expertise in the Law of the Sea. But let us contrast this political certainty with the actual knowledge of the Royal Navy Commander of the operation on which the captives were taken.

Before the spin doctors could get to him, Commodore Lambert said:

“There is absolutely no doubt in my mind that they were in Iraqi territorial waters. Equally, the Iranians may well claim that they were in their territorial waters. The extent and definition of territorial waters in this part of the world is very complicated”.

That is precisely right. The boundary between Iran and Iraq in the northern Persian Gulf has never been fixed. (Within the Shatt-al-Arab itself a line was fixed, but was to be updated every ten years because the waterway shifts, according to the treaty. As it has not been updated in over twenty years, whether it is still valid is a moot point. But it appears this incident occurred well south of the Shatt anyway.) This is a perfectly legitimate dispute. The existence of this dispute will clearly be indicated on HMS Cornwall’s charts, which are in front of Commodore Lambert, but not of Mr Blair.

Until a boundary is agreed, you could only be certain that the personnel were in Iraqi territorial waters if they were within twelve miles of the coast and, at the same time, more than twelve miles from any island, spit, bar or sandbank claimed by Iran (or Kuwait).

That is very hard to judge as the British government refuse to give out the coordinates where the men were captured. If they really are utterly certain, I find that incomprehensible. Everyone knows the Gulf is teeming with British vessels and personnel, so the position of units a few days ago can hardly be valuable intelligence.

Until a boundary is set, it is not easy to posit where it should be. It has to be done by negotiation or arbitration. I have participated in these negotiations, for example on the boundary between the Channel Islands and France.

With a dead straight coastline with no islands, and a dead straight border between two countries hitting the coast at a right angle, you could have a straight maritime border between the two running out from the coast at a right angle. This never happens.

In practice, you agree a series of triangulation points on both coastlines and do a geometric triangulation exercise to find a line running out from the coast. Coasts of course can be very odd shapes. Draw an imaginary coast and border on a bit of paper and try it yourself. You will soon see why the rules permit you to take into account the general trend of the coastline, and even the angle of the land border. Those are not problems of geometry but old fashioned horse trading.

First, of course, both sides will argue about which triangulation points on the coast to accept. You are allowed, for example, to draw a line across a bay entrance and use that as the coast, but there is plenty of room for the other side to argue over where that line is drawn.

That is only the start. For territorial seas (but not the 200 mile exclusive economic zone) uninhabited rocks and sandbanks count. Again huge room for argument here – the ownership of a useless sandbank is not necessarily a settled thing. Sticking your triangulation point on a sandbank twelve miles out can make a huge difference.

Then it really gets complex. What if the sandbank only appears at low tide? What if it is dry all day, but only at certain times of the year? What if it is prone to move about a bit?

You haggle like mad over this. “You can’t have that sandbank unless we have this one plus this spit.” You also then get into weighting. “That bit of land is only around half the time, so we’ll give it one third weighting” – in other words we will allow 33.3% more sea than you would get if it didn’t exist and we just used a point on the coast.

Massive volumes have been written on the prinicples behind these negotiations, but they tend to ignore the fact that ultimately it has to come down to political negotiating skills between a vast range of justifiable possible agreements. That is why we just can’t know where the boundary is between Iran and Iraq in this area, which has enough sandbanks to keep me happy thinking about it for centuries. If either side needs a negotiator…

Anyway, the UK was plainly wrong to be ultra provocative in disputed waters. They would be allowed to enter Iranian territorial seas in hot pursuit of terrorists, pirates or slavers, but not to carry out other military operations.

The Iranians had a right to detain the men if they were in seas legitimately claimed as territorial by Iran. Indeed, it is arguable that if a government makes a claim of sovereignty it rather has to enforce it, possession being nine parts of international law. But now the Iranian government is being very foolish, and itself acting illegally, by not releasing the men having made its point.

The story leaked by Russian intelligence claiming knowledge of US plans to attack Iran on 6 April has had great publicity in Iran, if very little here. Personally I doubt it is true. But it seems to me a definite risk that the Iranians will decide to keep the marines against that contingency.

That would be very unfortunate. The Iranian government, by continuing to hold the British personnel, are foolishly providing new impetus to Bush and Blair, whose attempts to bang the war drum against Iran have so far met profound public scepticism. We don’t need any more oil wars.

If Blair actually sought the release of our people, rather than anti-Iranian propaganda, he would stop making stupid macho noises and give an assurance that we intend to resolve not only this problem but all disagreements with Iran by peaceful means, and give specific reassurance that no attack is imminent.

But if the Iranian government wait for Blair to behave well, the marines will rot for ever. They should let the men (and woman) go now, with lots of signs of friendship, thus further wrongfooting Bush and Blair.