The husband of the British charity worker Nazanin Zaghari-Ratcliffe has delivered a Mother’s Day card to the Iranian embassy in London to mark the third year she has spent the celebration in jail.

Zaghari-Ratcliffe was arrested with her 22-month-old daughter Gabriella on 3 April 2016 at Tehran’s Imam Khomeini airport as she prepared to board a plane back to the UK after visiting family.

She was subsequently sentenced to five years in the city’s notorious Evin prison after being accused of spying, a charge she denies.

Speaking outside the embassy, Richard Ratcliffe said: “We’ve come to deliver her a Mother’s Day card, because obviously we can’t do that in person, and to deliver 155 bunches of flowers, one for each week she has been held.

“Flowers, partly because it’s a Mother’s Day tradition, also because that’s what people are given when they’ve been released from prison [in Iran].”

The foreign secretary, Jeremy Hunt, granted Zaghari-Ratcliffe diplomatic protection earlier this month. This means that from now on, an injury to her is viewed as an injury to the British state, though the move was dismissed by Iran. “It’s clear that Jeremy Hunt has taken a personal commitment to [my wife’s] case and he’s made some clear statements,” said Ratcliffe.

“Before he granted her diplomatic protection he went to Tehran. He’s done a lot to make it clear that he cares and this is a priority. He’s not done everything that we’ve wanted, but he’s also been clear that he’s not going to. As a family we’re appreciative of all he’s done.”

Speaking about his daughter, who is now four and living with her maternal grandparents in Iran so she can visit her mother, Ratcliffe said: “I spoke to Gabriella yesterday and there’s a prison visit today. We’re going to draw a card together for granny, my mum.”

When asked his wife’s mood, he said she was sometimes “in a dark place”. “Sometimes you speak to her and she seems fine, and sometimes she’s really bleak and dark and threatening all sorts of things – but yesterday she was fine,” he said.

Play Video 2:04 Nazanin Zaghari-Ratcliffe goes on hunger strike over being denied medical care in prison - video

In January, Zaghari-Ratcliffe staged a hunger strike in protest at being denied medical care. “She does threaten every so often that ‘I’ll do it again’ and it’ll be an escalation from last time,” said her husband. “I do live a bit in fear of what will happen.”

He added: “[The whole experience] has brought us closer together because we’ve had to survive it. I’m hugely proud of the fact that she’s kept going, she’s kept her dignity.”