British-Iranian dual national Nazanin Zaghari-Ratcliffe appeared in a Tehran court today to face new charges of "propaganda against the system", a week after she finished serving a five-year sentence, her lawyer said.

The hearing has dashed hopes of family and supporters for a swift release of the 42-year-old, in a case that has heightened diplomatic tension between London and Tehran.

"The hearing took place in a very calm and good atmosphere, in the presence of my client," said her lawyer Hojjat Kermani, adding that the judgment would be handed down at a later and unspecified date.

According to Mr Kermani, she is now being prosecuted for "propaganda against the system for having participated in a rally in front of the Iranian embassy in London" in 2009.

"Given the evidence presented by the defence and the legal process, and the fact that my client has also served her previous sentence, I hope that she will be acquitted," the lawyer added.

British Foreign Secretary Dominic Raab said: "It is unacceptable and unjustifiable that Iran has chosen to continue with this second, wholly arbitrary, case against Nazanin Zaghari-Ratcliffe.

"The Iranian government has deliberately put her through a cruel and inhumane ordeal.

"Nazanin must be allowed to return to her family in the UK without further delay.

"We continue to do all we can to support her."

Ms Zaghari-Ratcliffe was detained while on holiday in 2016 and convicted of plotting to overthrow the regime in Tehran, accusations she strenuously denied.

The mother-of-one was working at the time as a project manager for Thomson Reuters Foundation, the media organisation's philanthropic wing.

She has been under house arrest for months and had her ankle tag removed, giving her more freedom of movement and allowing her to visit relatives in Tehran.

She completed her sentence on 7 March.

A day later, her husband, Richard, and their six-year-old daughter, Gabriella, held a vigil outside the Iranian embassy in central London demanding she be allowed home.

He tried to deliver an Amnesty International petition signed by 160,000 supporters calling for his wife's release, but was turned away.

Earlier this month, Richard Ratcliffe told the BBC her detention has "the potential to drag on and on".

Media in both the UK and Iran and Mr Ratcliffe have drawn a possible link between Nazanin's detention and a British debt dating back more than 40 years.

The British government has previously admitted it owes Iran up to £300m, but both countries have denied any link with the Zaghari-Ratcliffe case.

She has been temporarily released from Tehran's Evin prison and has been under house arrest since the spring due to the coronavirus outbreak.

For four years, however, at Evin she spent time in solitary confinement in windowless cells, declared hunger strikes and had medical treatment withheld. 

While in prison, she suffered from lack of hygiene and even contemplated suicide, according to her husband.

Iranian authorities have consistently denied that Ms Zaghari-Ratcliffe was mistreated.

On Friday, campaign group Redress handed a report to Mr Raab, which it said "confirms the severity of the ill-treatment that Nazanin has suffered".

The legal campaigners said that it "considers that Iran's treatment of Nazanin constitutes torture".