Ever since the revolution in 1979, Iran's government has been difficult to deal with, resentful, inclined to behave in ways which other countries - particularly Western ones - find infuriating.
There has been a sudden upsurge in violence in southern Iraq
In spite of this, the British Foreign Office has tried over the years to keep talking.
This was partly from economic self-interest: Iran has always been a good market for British goods.
Partly it was for political reasons, since however irritating Iran can be, it is an important player in the region.
Last week, though, the British approach seemed to change. The UK prime minister, Tony Blair, accused Iran of involvement in attacks against the British military in southern Iraq.
"There have been new explosive devices used," he said, "not just against British troops but elsewhere in Iraq. The particular nature of those devices lead us either to Iranian elements or to Hezbollah."
Hezbollah is the Shia militia group in Lebanon which Iran supports.
Iraq's Prime Minister Ibrahim Jaafari disagreed:
"Some people want to harm the friendly relations between Iran and Iraq," he said, "but not only will Iraq not allow them to do so, it will continue to expand its relations with Iran."
The British policy of keeping on close terms with local politicians and local militia leaders, which worked quite well until the start of this year, is starting to collapse
Mr Jaafari is close to Iran - it sheltered him when he lived in exile from Saddam Hussein's Iraq, and it has strongly supported his party, Dawa.
But Iraq's President, the Kurdish leader Jalal Talabani, who has no record of support for Iran of any kind, also disagreed with Mr Blair. The Iranians he had spoken to denied it, he said.
Some very unpleasant things have certainly begun to happen in southern Iraq. The British policy of keeping on close terms with local politicians and local militia leaders, which worked quite well until the start of this year, is starting to collapse.
The militias have now thoroughly infiltrated Basra. Last May the police chief, Hassan al-Sade, told a Guardian correspondent he could only trust a quarter of his men.
An organisation several hundred strong is said to be operating within the Basra police force. Calling itself Jamaat, "the Assembly", it carries out sectarian attacks against Sunni Muslims and other acts of terrorism.
Tony Blair says the blame lies with Iran or Hezbollah
It was to Jamaat's headquarters in south-western Basra that two British SAS soldiers were taken after their abduction. British armoured vehicles attacked the building in an attempt to rescue them.
Several Shia groups are said to have links with Jamaat: the Fadila Party, which now controls the provincial government; the Badr Organisation, which is part of the Supreme Council for the Islamic Revolution (Sciri), the dominant force in the national Iraqi government; and the Mehdi Army, which supports the fierce but increasingly politically savvy cleric, Moqtada Sadr.
Shaped charges claim
So where does Iran fit into all this? It is probably safe to assume that each of these groups, Fadila, Badr and the Mehdi Army and the various splinters from them, has relations of some kind with Iran, the Shia power just a few dozen miles away across the border.
The British have always known this was happening, and had no great problem with it. In fact, in the past, British officials maintained that Iran tended to have a calming effect on the militias and political groupings.
Has this changed now? Is Iran encouraging the groups which carry out attacks on British troops, as Mr Blair implies?
If Iran is less helpful towards the British in Basra than it used to be, then life there is going to be even harder
The evidence, as far as we know, relates to what are called shaped explosive charges. These are relatively new to Iraq, yet they aren't particularly new in themselves.
There will probably have been shaped charges in the arms depots of Saddam Hussein's army - depots which have been systematically looted.
Or maybe Iranian agents have indeed borrowed these charges from Hezbollah and brought them across to Basra. But it is far from conclusive.
The deterioration of the situation in Basra and the south has been a serious blow to the British government.
Before it happened, British officials were able to defend their presence there as something of clear benefit to the inhabitants.
The British soldiers were popular with most local people, and life was far easier there than in the areas controlled by the Americans.
Iran denies links to the attacks on British troops
That has changed now, and there is a natural temptation to blame it all on outside agents.
The British only managed to run Basra peacefully for so long because of their experience in dealing with complicated political situations, and their tactfulness among local populations. That effect now seems to have worn off.
If Iran is less helpful towards the British in Basra than it used to be, then life there is going to be even harder.
The British Foreign Office, under Jack Straw, seems less concerned than Mr Blair to play the blame game.
"We look to the Iranian government to sit down with us, hear what we have to say, and take action where appropriate," he said after Mr Blair had made his accusations.
The fact is, the British will not be in Basra much longer, but Iran will be always a looming presence across the Shatt-al-Arab, the southern part of Iraq at the very north of the Gulf.
If Britain wants to continue helping southern Iraq, it has to keep talking to Iran: firmly, and from a position of strength, but not threateningly.
There is, as Margaret Thatcher used to say, no alternative.
There is a mistrust between the western countries and Iran caused by the event of the modern history. Unfortunately this has and will always affect the interest of all sides in a negative way. In the case of the UK for most Iranians regardless of their political views, this mistrust is deep routed due to historical events of late 1800 up to the modern day. I believe the only way solutions could be found is when all sides start to talk to each other without preaccusations and preconditons and try to find solutions which will meet everyone's interest.
Nozar Basseri, Cork, Ireland
Mr. Simpson's comment are very typical of the tried and failed politics of pacification that the western world has adopted since Chamberlin in 1938. The only statesman since that has had the foresight and courage to say,no,enough is enough, has been Sir Winston Churchill. All the time the Mr.Simpson's of the world keep up this stance the more and heavier the demands will be made by countries such as Iran as they only perceive appeasement as weakness.
Michael Mciver, Hastings England
The Americans and the British, for that matter have long prided themselves with having the most imaginative modes of "blowing things up". And now it seems they are accusing Iran of finding an entirely new way of "blowing things up"? So much so that it is actually a "fingerprint"? Come now, exactly how does this differ?
Simpson says that these "shaped charges" have long existed, so how does Mr. Blair explain himself this time?
Bramdean, North Carolina, USA
British officials should know that Iranians and Iraqis have a cultural relationship which sometimes extends to politics, even after the Iran-Iraq war the Persians of Iran and the Arabs of Iraq are culturally bonded and with the fall of saddam these two nations are going to be good allies but British and US officials will do anything to make these two countries distrust each other at a sensible in a unstable region.
And western nations such as the UK and the US cant stand the fact that the only nation who benefited from Saddam fall without a price is Iran which is the biggest critic of western countries.
Mehdi Moustafa , Baghdad, Iraq
Does Alee from New York not realise that John Simpson is a journalist, not a politician, and that he is simply trying to express his objective view of the situation.
Kieron, UK overseas, Washington D.C.
In my opinion the present Iranian govenment does not want a stable and democratic Iraq. The west must be firm on its stance. This Islamic regime does not understand the language of moderation. The majority of Iranians think the USA approach is far better than the British.
Majidian, Isfahan, Iran
It's appalling that a Brit can write an article implying that England must keep talking with Iran even if it is helping to blow up Britich soligers. Does Iran deserve the benefit of the doubt that it is not involved in the bombings? This just shows the silliness of applying common legal principles in the context of state relations and acts of War. Iran is a cancer in this world. Terrorizing its own citizens is bad enough - terrorizing others should not be tolerated.
I think history will decide that the West fell after WWII because the majority of Europe decided that nothing was worth fighting to save and no indignity was beyond the pale. I think we in the West are lost.
Scott Lewis, Chicago, IL USA
One does rather wonder why the neo-cons, who decided to depose Saddam and impose democracy on Iraq, were so keen to strengthen Iranian influence in the Middle East.
Or did they really not see that coming?
Philip, Rotherfield UK
As an Iranian who lives in the west and visits the country every year, I firmly believe that the occupiers of Iraq have missed the simple fact that people in the Middle East don't tolerate being occupied by a foreign country, It has been nearly 3 years now and improvements are not taking place with the speed they should, people are tired of the insecurities that exist. They leave the house not knowing whether their going to get blown up on the day by some loony brain washed Wahabi and then you also get the so called undercover British agents being caught with explosives. Now it's easy to blame others but the main problem is that people are tired of the occupation of their beloved country. The message is one cannot accuse others of meddling in one's affairs when they themselves occupied the country in the first place . If they like the Iranians let them be, you cannot decide for a nation who to like and who to dislike!
Mohammad N, London, UK
Politics are like ropes tying nations together. It's all about compromising. London should not expect by leading the EU opposition in the Iranian nuclear negotiations, that its troops' lives will be the same inside Iraq. This is quite obvious. Everyone plays his own cards to his advantage. Also, without solid proof on accusations, it only complicates matters unnecessarily, and is considered unwise and a behaviour unbecoming of one of the world leaders. It is a weak sign.
Ahmed Kamel, Cairo, Egypt
There is of course the elephant in the room bearing some comment: this situation stems directly from the ill-fated decision to go into Iraq in the first place. Britain would not be compelled to deal with such issues with Iran under such circumstances if its forces never entered. The scale of this dark situation is only larger for the United States. The US misplayed a good hand into misguidedly pinning down thousands of Americans next to Iran (not to mention Syria and Saudi Arabia).
Manuel DePiedra, San Francisco
Britain and the US are seeking a viable Iraq exit strategy. To facilitate this a co-operative Iran will be indispensable. In this light, Mr Blair's comments appear somewhat rash.
David A. Greenslade, Paris, France
Your observations are both accurate and wise but wisdom and accuracy are strangers to this miserable situation. The abiding tragedy of Iraq is that those who understood least had the power and those who understood most were ignored. One sadly suspects that in dealing with Iran this trend will continue.
kennedy, Brighton England
Talking firmly is the correct answer to this complex situation. It should be noted that Iranians who are leading the country at this historical moment, have their roots in populace and traditional background, meaning that by nature and upbringing they bow to authoritarian calls - only. As long as you appear powerful they are on your side. Talking democracy and soft power prepares the ground for further abusive behaviour from their part as they have become extremely manipulative. Iran is a country ruled by lumpen dictatorship - you have to know the language.
Nasrin Azadeh, Oxford - UK
Whatever the Iranians might say in public about wanting stability in Iraq, their strategic interest lies in making the occupation as difficult as possible. After all, we're the ones who invaded two of their neighbours and are now threatening military action against them, so what do Bush and Blair expect them to do, invite us to tea? The more it costs the western allies in blood and money to occupy Iraq, the less likely we are to try "regime change" again in Iran
Raphael Starr, Princeton, New Jersey!
The hardliners that govern present day Iran were conceived decades ago through misguided British and American foreign policy that valued oil over the democratic will of a sovereign nation.
Farid John Ghadessy, Singapore
So long as Iran is being threatened on a daily basis and pressured on the international scenes by the very powers that are accusing it of meddling in Iraq, Iran will do what it takes to secure its interests in the region. The sooner international community accepts Iran for what it is, a nuclear power in the making, the better it'll be for all the region. By the way, how convenient to cover up the two British "special forces in the Arabic outfits" with accusations against Iran?
Interesting timing there.
Iran can be co-operative only at a price the West can not afford, i.e. a nuclear Iran, so things ought to be getting worse and worse.
F.Bakhtiar, Mehr Shahr, Karaj, Iran
What proof does Mr Blair have in claiming that Hezbollah was involved? I'm no fan of theirs, but they have hitherto confined themselves to Lebanon, where they also take part in elections, hardly the average terrorist stuff.
Iraq's future is influenced by US, Iran, and Britain. This is the reality of the situation and its wise for US and Britain to recognize this fact. Cornering Iran will not work and it can only prolong settlement of Iraq's political structure.
Barry, Anaheim, USA
Just as America and Israel are the Arabs' favourite bogeyman, so too, Iran is America's favourite bogeyman. They need Iran to blame their shortcomings on to. Nobody believes that they are innocent of everything, but they cannot be guilty of everything they are accused of. Britain needs to wisen up to that, and stop repeating the Washington Mantra.
Ammar Shams, London, England
I'd have loved to live long enough to see every nation dicuss its needs in Congress with every other nation, and settle differences through discussion and acceptance of majority votes. Alas, I'll die in despair
Do you honestly think that the key to solve this aggresive behavior from Iran is to talk firmly? The Iranians not only provide money and technology to kill the soldiers, Iraqis and their allies, but they are eagerly doing the same thing elsewhere in the world, according to intelligence service from western countries. Talking firmly to a country that are supporting the deaths of your people in service abroad is hardly the key. But on the other hand politicians like you keep thinking business before the lives of the young people. It surprise me that somebody with your experience talks about talking firmly to a country that is one of the biggest police states in the world.
Alee , New York