London mayor Sadiq Khan has called for the release of jailed charity-worker Nazanin Zaghari-Ratcliffe.
Mr Khan met Mrs Zaghari-Ratcliffe's husband Richard and offered his support in urging the Iranian authorities to release her in time for Christmas.
The British-Iranian, who turns 40 on Boxing Day, was jailed for five years in 2016 after being convicted of spying, which she denies.
Mr Khan described her imprisonment as a "travesty of justice".
He said: "Nazanin has been wrongly detained in an Iranian prison for over two years. She has done nothing wrong, has broken no laws. The charges against her are completely false.
"We - and indeed the whole country - know what a travesty of justice it is that Nazanin continues to be detained.
"With Christmas approaching, we are calling on the Iranian authorities to release her at once so she can return home and be reunited with her family."
Ms Zaghari-Ratcliffe was arrested at Tehran airport in April 2016 after visiting her family on holiday. She has always maintained the visit was to introduce her daughter Gabriella to her relatives.
The mother-of-one from Hampstead, north London, was recently reunited with her four-year-old daughter during a three-day temporary release.
But since returning to prison, after her application for an extended release was denied, she has suffered several panic attacks.
Theresa May met the Iranian president for talks at the United Nations in New York in September where she told Hassan Rouhani she had "serious concerns" about Mrs Zaghari-Ratcliffe's imprisonment.