Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori were released as major powers in Vienna close in on renewing the landmark 2015 Iran nuclear deal.
Two British-Iranians flew home leaving Tehran following nearly 'six years of hell' in detention in Iran as they prepare to be reunited with their family.
The UK government also confirmed it had paid a longstanding debt over a cancelled defence contract.
"Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori will return from Iran today," British Foreign Secretary Liz Truss said. "They will be reunited with their families and loved ones."
UK lawmaker Tulip Siddiq, who represents the north London district where Zaghari-Ratcliffe's family live, tweeted a photo of her constituent smiling on board a plane.
"It's been 6 long years - and I can't believe I can FINALLY share this photo," she wrote.
"Nazanin is now in the air flying away from 6 years of hell in Iran," she added.
It's been 6 long years - and I can't believe I can FINALLY share this photo.— Tulip Siddiq (@TulipSiddiq) March 16, 2022
Nazanin is now in the air flying away from 6 years of hell in Iran.
My heart goes out to Gabriella and Richard, as her long journey back home to them gets closer by the minute.#NazaninIsFree ❤️ pic.twitter.com/BzEEBP840C
Zaghari-Ratcliffe's husband Richard Ratcliffe told AFP at the family home that "the first thing she always wanted to do was me make her a cup of tea".
"I'm relieved that the problems were solved," he said, standing next to their young daughter Gabriella, adding that the government should make sure "it doesn't happen again".
Truss also announced that Morad Tahbaz, an Iranian-American who also holds British nationality, has been released from prison "on furlough" to his Tehran home.
The pair were released as major powers in Vienna close in on renewing the landmark 2015 Joint Comprehensive Plan of Action (JCPOA) on regulating Iran's nuclear programme.
The deal gives Iran sanctions relief in exchange for curbs on its nuclear programme and Tehran said on Wednesday that "two issues" remain with the US to restore the deal.
Truss confirmed that, with diplomatic assistance from Oman, London and Tehran had "in parallel" resolved a $515-million debt dating back to the 1970s and the era of the Shah of Iran.
The UK has consciously avoided saying the detention of the pair, and others held in Iran, was linked to the debt for an order of tanks that was cancelled after the 1979 Islamic revolution.
Foreign Minister Hossein Amir-Abdollahian said on Wednesday that Iran had received the money "a few days ago", adding that it was "wrong to link Iran receiving its debt... to the release of these people".