The UK Foreign Office advises against all travel to Iran, saying British and British-Iranian dual nationals are at “significant risk of arrest, questioning or detention”.

Having a British passport or connections to the UK “can be reason enough for the Iranian authorities to detain you”, it adds.

The Foreman family said the couple’s detention was a “distressing situation” and they are “deeply focused on ensuring their safety and wellbeing during this trying time”.

Responding to the case, Mr Ratcliffe told the PA news agency: “My heart goes out to them, and I hope they are not in for a long ordeal, and that the government is able to respond more promptly than it did in our case.

“I do think the risks would be a lot clearer to people if the UK travel advice to Iran talked about the risks of hostage-taking. People would be more alert to the fact that it is not personal, and it doesn’t matter whether you have travelled there with a good heart.”

Posting on Instagram before being detained, Mrs Foreman acknowledged travelling to Iran, against Foreign Office advice, and to Pakistan was risky and “slightly scary”.

But she wrote “we know the rewards of meeting incredible people, hearing their stories, and seeing the breathtaking landscapes of these regions could far outweigh the fear”.