Former foreign secretary Jeremy Hunt has said the UK Government “should absolutely pay” a £400m debt it owes to Iran in order to help free British nationals imprisoned there, such as Nazanin Zaghari-Ratcliffe.

Appearing on Sky News this morning, Hunt described Iran's regime as "horrible" but the deal would be necessary to secure the release of Zaghari-Ratcliffe.

The money owed relates back to the 1970s when the Shah of Iran signed a contract ordering 1,500 state-of-the-art Chieftain battle tanks and 250 repair vehicles costing £650 million from the UK.

An issue came up in 1979 when, with just 185 tanks delivered to Tehran, the Iranian Revolution deposed Shah Pahlavi and installed an Islamic Republic.

The UK cancelled the undelivered part of the order, and Iran wanted their money back.

It was eventually ruled by an international court that the UK owed Iran the large sum, but with it still having not been paid yet it has been seen as a blockage in the release of political prisoners that Iran holds.

Hunt said on Sky News: "We established that this is not paying ransom money.

"This is paying a debt that an international court has said we owe, that the defence secretary has said we owe, and I think there is now no argument about the principle of it.

"It's difficult. Iran is a horrible regime that does the most despicable things, so it doesn't make anyone comfortable doing it, but now it's about the mechanics."

As well as Zaghari-Ratcliffe, Iran currently holds two other British nationals in Anoush Ashoori and Morad Tahbaz on alleged espionage or spying charges.

Zaghari-Ratcliffe's husband Richard is currently protesting outside the Foreign Office on a hunger strike to put pressure on Boris Johnson to meet with Iran's officials at COP26 to try and make a deal.