LONDON — “I am entirely alone in Iran,” she wrote in one letter. “In addition to all the pain I have endured here, I feel like I am abandoned and forgotten.”

Those words were written by a British-Australian academic, Kylie Moore-Gilbert, who has been held in an Iranian prison for more than a year — including long stretches of solitary confinement — in a series of letters published by British news outlets this week.

Ms. Moore-Gilbert was detained in Iran in September 2018 while attending a conference. She was later convicted of spying and sentenced to 10 years in prison. She is being held in Evin Prison in Tehran in solitary confinement in a high-security wing run by the Islamic Revolutionary Guards Corps.

Detailing the harrowing conditions, Ms. Moore-Gilbert wrote about her deteriorating health, begged to be released from the wing where she had spent much of her time behind bars and rejected bids by the Iranian authorities to recruit her as a spy.