An Australian journalist – held in detention in China for three years as of this weekend – has spoken publicly for the first time.

“I miss the Sun. In my cell, the sunlight shines through the window, but I can stand in it for only 10 hours a year,” Cheng Lei said in an open letter to the people of Australia, dictated to diplomats who are able to speak to her each month.

“I can’t believe I used to avoid the sun when I was living back in Australia… It’ll probably rain the first two weeks I’m back in Melbourne,”

“I haven’t seen a tree in three years,” she said.

The finance reporter was working for China’s state media English-language television station CGTN when she was picked up, spending her first six months of detention in solitary confinement without charge.

In March last year, Ms Cheng was tried in secret and has been waiting for a year and four months to be sentenced.

Australia’s ambassador to China, Graham Fletcher, tried unsuccessfully to gain entry to the court to witness proceedings.

Even her family is not aware of what she is accused, other than that it is said to involve passing on “state secrets”.

In China, what constitutes a state secret is a very vague concept and can involve anything which the government deems to be sensitive.

The letter released today is filled with nostalgia of her life in Australia, the country her family immigrated to from Hunan Province when she was just 10 years old.

“In 1987, I remember camping for the first time with my family, my dad driving a $700 [£550] car,” she said.

“I relive every bushwalk, river, lake, beach with swims and picnics with psychedelic sunsets, sky that is lit up with stars, and the silent and secret symphony of the bush.”

In prison, the former TV anchor said that she “secretly mouth[s] the names of places I’ve visited and driven through” in Australia.

In what she describes as “a love letter to 25 million people”, Ms Cheng said she recalls the kindness of strangers and friends alike and that the memories of such kindness “have come back to me now and restored me” behind bars.

She said she misses sea salt, black humour, the Queensland tropics and the never-ending blue skies of Western Australia, as well as the sand between her toes.

There has been some speculation that the sentencing of Ms Cheng has been delayed so that her case can be used as a bargaining chip in the Chinese government’s dealings with its Australian counterpart.

Australian Prime Minister Anthony Albanese has been invited to Beijing to meet Xi Jinping. However, he is coming under considerable pressure at home not to make the trip until Ms Cheng and fellow Australian Yang Hengjun have been released.

The end of her letter contains probably the most important line: “Most of all, I miss my children.”