Britain's national security adviser, Jonathan Powell, attended the final talks between the US and Iran and concluded that Tehran's offer on its nuclear programme was significant enough to avert a rush to war, sources have revealed.
Mr Powell was present at the Oman-mediated talks in Geneva in late February, judging the Iranian proposal 'surprising' and believing progress had been made. He brought an expert from the UK Cabinet Office, amid concerns about the technical expertise of US representatives Jared Kushner and Steve Witkoff.
One western diplomat said Mr Powell thought a deal was achievable, though Iran had not yet fully met demands on UN inspections. A former official said the UK team was surprised by what Iran put on the table, describing it as not a complete deal but progress unlikely to be Iran's final offer.
The next round of talks was due in Vienna on 2 March, but never took place. The US and Israel launched an all-out attack two days earlier. The UK has since regarded the attack as unlawful and premature, believing diplomatic options had not been exhausted.
The UK's reluctance to support the US attack has strained relations with Washington. Prime Minister Sir Keir Starmer was criticised by President Trump for initially refusing to allow US use of British military bases, later permitting them for defensive purposes. Mr Powell's attendance at the talks helps explain the government's position.
Mr Powell, a former chief of staff to Tony Blair, has long experience as a mediator. His access to the talks may reflect his relationships in Washington. Downing Street declined to comment. The talks were mediated by Oman's foreign minister, Badr bin Hamad Al Busaidi.
