Richard Dalton: Relations will only improve when it benefits Tehran

Foreign Minister Mottaki's promise of a smack in the mouth is colourful, but it's nothing new: using metaphors of violence can be second nature for some Iranian politicians, as a review of the Tehran press shows every day.

But Britain should not aim for an easier ride by taking a softer line on the internal tensions in Iran – that would be wrong in principle and would not work.We cannot ignore repression.

Nor can we force Iran to come up to the mark we set. The only approach that has a chance of succeeding is the unglamorous one of being true to our core values, an approach based on patiently and persistently seeking mutual advantage despite the continual setbacks. Iranians expect it of us.

Britain's relations with the Islamic Republic of Iran have always been fraught. Besides the disputes and disagreements, some of which make the headlines, the Iranian Government considers that we are hostile to their revolution and an obstacle to their foreign policy. They consider that we are deceitful in our intentions and our methods, that we are militaristic and colonialist, that we are responsible for cultural invasion, that we are promoting a return to the old despotic order in Iran, that we oppose the Government's economic plans, and that we are encouraging monarchists and separatists to commit bomb outrages and instigate soft overthrow. It can get personal – our ambassador has been described as a master of spies and a string-puller; or absurd – alleged tunnels under the street to allow the embassy staff to bring in prostitutes.

In 2002 and 2003 Jack Straw tried in vain to get beyond these complexes, in the hope of building on the many common interests we had and still have with Iran.

That does not mean that our strategy was wrong.We failed partly because our policies – including on human rights – were irreconcilable with Iran's, partly from lack of leverage, and partly because at the top level Iran was not ready to find a way through.

In the end, our hopes of change are in the hands of Iran's decision makers. They have to consider it in their nation's interest to change. Only then will our relations with Iran develop their full potential.

Sir Richard Dalton was British ambassador to Iran from 2002-06