The British government has appointed a new ambassador to Iran in the latest sign of increasingly friendly relations between the two countries.

Just days after British Airways announced a resumption in flights to the Islamic Republic, Nicholas Hopton, who is Britain’s Chargé d’affaires in Tehran, was appointed ambassador in what was described as “an important step forward”.

Hopton is no stranger to the region, having previously been British ambassador in Qatar and Yemen, following a spell in Morocco. He said he was “delighted” with the appointment, adding: “I look forward to the next phase of cooperation.”

News of the continuing rapprochement will provide no comfort to Israel’s supporters in the UK, who remain convinced that Iranian state-funded terrorism targets Jews in Israel and around the world.

Foreign Secretary Boris Johnson welcomed Hopton’s appointment as an “important moment,” saying the upgrade in diplomatic relations would increase dialogue, alluding to the role Iran plays in Syria, Lebanon, Yemen, Iraq and the Gulf States.

“I hope this will mark the start of more productive cooperation between our countries, enabling us to discuss more directly issues such as human rights and Iran’s role in the region, as well as ongoing implementation of the nuclear deal and the expansion of the trading relationship between both our countries.”

However, he said the British government still had concerns about a number of dual nationals, including British mother Nazanin Zaghari-Ratcliffe, a charity worker who was arrested and imprisoned while on her way back to the UK on 3 April.

A project manager for Thompson-Reuters’ charitable arm, the 37-year old is understood to have been kept in solitary confinement, with lawyers and British officials denied access, because Iran does not recognise dual citizenship.

Johnson said he had expressed his “deeply concern” to Iranian Foreign Minister Mohammad Javad Zarif. Only last month, Prime Minister Theresa May pressed the case in a phone-call to Iranian president Hassan Rouhani, in which they also discussed concerns following the nuclear deal struck in Geneva last year

In return for neutering its nuclear programme, Iran was promised sanctions relief, but banks have so far resisted transactions with Iranian entities for fear of falling foul of America’s remaining sanctions, which cover organisations linked to the Iranian Revolutionary Guards.

In her conversation with Rouhani, May promised to help free up the flow of cash into Iran. A Downing Street spokesperson said: “The Prime Minister underlined that the UK would continue to play an active role in support of full implementation of the deal, including efforts to enhance banking cooperation between the UK and Iran.”