Patrick Wintour and Julian Borger – The Guardian March 17, 2026

Britain’s national security adviser, Jonathan Powell, attended the final talks between the US and Iran and judged that the offer made by Tehran on its nuclear programme was significant enough to prevent a rush to war, the Guardian can reveal.

Powell thought progress had been made in Geneva in late February and that the deal proposed by Iran was “surprising”, according to sources.

Two days after the talks ended, and after a date had been agreed for a further round of technical talks in Vienna, the US and Israel launched the attack on Iran.

Powell’s presence at the talks, and his close knowledge of how they were progressing, was confirmed by three sources.

One source said he was in the building at Oman’s ambassadorial residence in Cologny, Geneva, acting as an adviser, reflecting widespread concern about the US expertise on the talks represented by Donald Trump’s son-in-law Jared Kushner and Steve Witkoff, Trump’s special envoy on several issues.

Kushner and Witkoff met with Netanyahu in the days before the U.S./Israeli strike on Iran. Click to enlarge

Kushner and Witkoff had invited Rafael Grossi, the director general of the International Atomic Energy Agency (IAEA), to the Geneva talks, to provide technical expertise, though Kushner would later claim that he and Witkoff had “a pretty deep understanding of the issues that matter in this”.

Nuclear experts would later say that Witkoff’s pronouncements on the Iran nuclear programme were riddled with basic errors.

Powell has long experience as a mediator, and one source said Powell brought an expert from the UK Cabinet Office with him. One western diplomat said: “Jonathan thought there was a deal to be done, but Iran were not quite there yet, especially on the issue of UN inspections of its nuclear sites.”

A former official who was briefed on the Geneva talks by some of the participants said: “Witkoff and Kushner did not bring a US technical team with them. They used Grossi as their technical expert, but that is not his job. So Jonathan Powell took his own team.

“The UK team were surprised by what the Iranians put on the table,” the former official added.

“It was not a complete deal, but it was progress and was unlikely to be the Iranians’ final offer. The British team expected the next round of negotiations to go ahead on the basis of the progress in Geneva.”

That next round of talks was due to take place in Vienna on Monday 2 March, but never happened. The US and Israel had launched their all-out attack two days earlier.

Powell’s attendance at the Geneva talks, as well as at a previous set of meetings earlier in the month in the Swiss city, helps in part to explain the UK government’s reluctance to back the US attack on Iran, a reluctance that has put the UK-US relationship under unprecedented strain.

The UK saw no compelling evidence of an imminent threat of an Iranian missile attack on Europe, or of Iran securing a nuclear weapon. This is the first time it has become clear that Britain was so closely involved in the talks, and so had good reason to decide whether diplomatic options had been exhausted and a US attack was necessary.

Instead the UK regarded the attack as unlawful and premature since Powell believed the path remained open to a negotiated solution to the long-running issue of how Iran could reassure the US that it was not seeking a nuclear weapon.

Downing Street declined to comment on Powell’s presence at the Geneva talks or his view of them.

Keir Starmer has been repeatedly lambasted by Trump for not doing more to support the US attack, including by initially refusing to let America use British military bases, and only allowing them to be used later for defensive purposes after Iran started attacking UK Gulf allies.

Trump has warned it could be bad for Nato if its European member states do not answer his call to help open the strait of Hormuz, a demand that has been declined.

The indirect talks in Geneva between Iran and the US were being mediated by Oman’s foreign minister, Badr bin Hamad Al Busaidi.

Gulf diplomats did not specify on what basis Powell had been given access to the talks, but it may reflect the relationship he has managed to build with the US over the years, including previously as chief of staff to Tony Blair.

UK officials have subsequently explained they were impressed that Iran was prepared for the deal to be permanent and, unlike the 2015 nuclear agreement, would not have cut-off dates, or sunset clauses ending the restrictions on its programme.

Iran had also agreed to down-blend the 400kg stockpile of highly enriched uranium under the supervision of the IAEA inside Iran. It agreed no stockpiles of highly enriched uranium would be built up in the future.

In the final session of the talks, Iran agreed to a three- to-five-year pause on domestic enrichment, but the US in the afternoon session, after consultations with Trump, demanded a 10-year pause.

In practice, Iran had no means to enrich domestically because of the bombing of its enrichment plants in 2015.

Iran had also made an offer of what the mediators described as an economic bonanza, with the US being given the chance to participate in a future civil nuclear programme.

In return, nearly 80% of the economic sanctions on Iran would have been lifted, including assets frozen in Qatar, a demand Iran made in the 2025 talks.

The Oman mediator believed the offer of zero stockpiling of highly enriched uranium was a breakthrough that meant an agreement was within reach.

Accounts differ on whether Kushner left the talks giving the impression Trump would welcome what had been agreed, or that the US negotiators knew it would take something massive to persuade Trump that war was not the best option.

One diplomat with knowledge of the talks said: “We regarded Witkoff and Kushner as Israeli assets that dragged a president into a war he wants to get out of.”

The Guardian’s report that Powell was in the room during the talks was cited in parliament on Tuesday by Liz Saville Roberts, an MP for the Welsh nationalist Plaid Cymru party, during an update by Britain’s foreign secretary, Yvette Cooper.

“It appears diplomatic options were still viable and there was no evidence of an imminent missile threat to Europe or of Iran obtaining a nuclear weapon,” Saville Roberts told Cooper.

“Does she therefore believe a negotiated path between Iran and the US was still possible at that time and, if so, surely that means that the initial US and Israeli strikes were premature and illegal?”

Cooper responded: “The UK did provide support for negotiations and diplomatic processes around the nuclear discussions.

“We did think that was an important track and we did want it to continue. That is one of the reasons for the position we took on the initial US strikes that took place.”

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