Into the 18th day of his second hunger strike Richard Ratcliffe called on Boris Johnson to “deliver on his promises”.

Richard urged the prime minister to meet an Iranian delegate at the COP26 climate conference to demand the freedom of Britons detained in Evin prison – including his wife, Nazanin Zaghari-Ratcliffe.

The West Hampstead resident was joined at his protest camp outside the Foreign Office by Strictly Come Dancing co-host Claudia Winkleman and writer Victoria Coren Mitchell, and on Tuesday by Sir Keir Starmer.

Nazanin is detained over allegations, which she denies, of plotting to overthrow the Tehran government, having been arrested in 2016.

Richard says his wife is being held “hostage” due to the UK owing a £400 million debt to Iran over a failure to deliver Chieftain tanks. An international arbitration process in 2008 ruled that the UK owes Iran the debt.

Ham & High: Richard Ratcliffe with Claudia Winkleman (left)and Victoria Coren Mitchell (right)Richard Ratcliffe with Claudia Winkleman (left)and Victoria Coren Mitchell (right) (Image: PA Wire/PA Images)

“The Iranian delegate needs to be asked about it," Richard said. "The prime minister promised to settle a debt and he hasn’t, and now my wife is being held hostage. He needs to deliver on that promise."

Mr Ratcliffe, who previously completed a 15-day hunger strike, says he is “now in uncharted territory” and is seeing the physical effects of 16 days without food, including experiencing cold hands and feet.

He said: “It’s definitely getting harder. My family are worried about how long it will go on for.”

Ham & High: Richard Ratcliffe with his mother BarbaraRichard Ratcliffe with his mother Barbara (Image: Linda Grove)

Mr Ratcliffe says he is watching for various physical symptoms that are to be expected the longer a hunger strike goes on for, including becoming dazed and dizzy, losing weight and his skin turning yellow.

Hampstead and Kilburn MP Tulip Siddiq told the Ham&High the government needs to "wake up to the fact" that Nazanin has been separated from her family for more than six years.

Ms Siddiq said: “Nazanin has been told that her imprisonment is directly linked to our failure to pay the money so until we pay the money back their family won't be reunited. So essentially we’re making an innocent woman pay for our failure to pay the debt, which is shameful."

The MP said the case "won't move on" until the government publicly recognises Nazanin as a hostage. Labour leader Sir Keir Starmer, who also visited Richard, said: “I hope that we meet again in different circumstances. There is cross-party support to get you through this.”

As the Ham&High went to press Richard was set to begin his 19th day on hunger strike.

Ham & High: Labour leader Keir Starmer (left) and Labour MP Tulip Siddiq (right) meet with Richard RatcliffeLabour leader Keir Starmer (left) and Labour MP Tulip Siddiq (right) meet with Richard Ratcliffe (Image: PA Wire/PA Images)