Julian Borger writes: In May 2003, when the Bush administration’s might was at its zenith, a Swiss diplomat called Tim Guldimann arrived in Washington carrying an extraordinary message.

As Switzerland’s ambassador in Tehran, Guldimann’s job was to represent the interests of the United States, which had no embassy, and that was he thought he was doing. The letter he was carrying was an offer of comprehensive negotiations from the Iranian government. In return for a lifting of US sanctions and the handing over of members of a US-designated Iranian terrorist group, Tehran was willing to place its nuclear programme under an intrusive monitoring and inspection regime, end armed support for Hamas and Hizbullah, and accept a Saudi plan for Israeli-Palestinian peace.

In short, Iran was ticking just about every box on the American diplomatic wish-list. So what happened? Dick Cheney and Donald Rumsfeld rejected the offer out of hand. “We don’t speak to evil,” was the official line. Not only was Guldimann sent packing, the Bush administration actually reprimanded the Swiss for over-stepping their diplomatic mandate.

The depressing fiasco is the opening scene of a perfectly-timed new book, A Single Roll of the Dice, by Trita Parsi, a carefully balanced and thoroughly researched account of the tortured US-Iranian relationship in recent years.