Broadchurch actress Olivia Colman wiped tears away as she stood alongside Benedict Cumberbatch while performing at a literary event hosted inside Her Majesty's Prison in Brixton.
The British stars joined a string of personalities in reading famous letters to an audience from inside the prison chapel as part of a Letters Live special broadcast to 110 prisons across England and Wales in support of the 10th anniversary of the Prison Radio Association.
Cumberbatch read a letter written by the late singer Leonard Cohen to his muse and former lover Marianne Ihlen, who inspired one of his most famous hits, the 1967 song So Long Marianne.
The Canadian singer and songwriter, who died aged 82 last month, wrote a letter to Ihlen in July this year, which was reportedly read to her on her deathbed just days before she died aged 81.
Colman, who was nominated for a Golden Globe for The Night Manager earlier this week, became emotional as she read the reply to Cohen's letter, written by a friend of Ihlen's, at the event held at the South London prison.
The touching letter from Cohen said: "Well Marianne, it's come to this time when we are really so old and our bodies are falling apart and I think I will follow you very soon. Know that I am so close behind you that if you stretch out your hand, I think you can reach mine."
Ihlen's friend replied writing that Marianne had "slept slowly out of this life yesterday evening. Totally at ease, surrounded by close friends."
"Your letter came when she still could talk and laugh in full consciousness. When we read it aloud, she smiled as only Marianne can. She lifted her hand, when you said you were right behind, close enough to reach her," the letter said.
It ended poignantly on the famous lyrics penned by Cohen himself: "So long, Marianne."
The letters were just two of a series of memorable letters read by famous names that also included comedian Russell Brand, actor Mark Strong and television presenter Mariella Frostrup.
They were also joined by former prisoners who read letters that have been sent to National Prison Radio (NPR) over the years.
The first Letters Live event was held in December 2013, and was inspired by Shaun Usher's best-selling Letters Of Note series and website, as well as Simon Garfield's book To The Letter.
Brand drew laughs a plenty as he read the letter of complaint written in 1932 by comedian Fred Allen to the State of New York Insurance Department, documenting his dissatisfaction with the compensation he'd received from an insurance company.
Poet and spoken word artist Kate Tempest received a standing ovation after she read an extract from her own award-winning piece titled Brand New Ancients.
Strong, the star of films such as RocknRolla and The Imitation Game, read a letter written by British philosopher Bertrand Russell in 1918, while he was an inmate at Brixton prison, after being imprisoned for his anti-war lectures and writings.
Russell was only allowed to write one letter a week, but disguised letters to his lover by writing in French and claiming they were chapters of a book he was penning.
Clarke Peters, star of popular American TV show The Wire, read two letters, one of which included pairing up with Tempest.
The twosome read the correspondence between American singer Iggy Pop and a 21-year-old fan named Laurence, who later revealed the letter arrived at her home in Paris on the morning her family were being evicted by bailiffs.
Pop replied to the 20-page letter penned by Laurence, saying: "thank you for your gorgeous and charming letter, you brighten up my dim life. i read the whole fucking thing, dear. of course, i'd love to see you in your black dress and your white socks too. but most of all i want to see you take a deep breath and do whatever you must to survive and find something to be that you can love."
The first letter read by Peters was written by American novelist, playwright and poet James Baldwin, who Peters said was a close friend of his.
National Prison Radio is the world's national radio station for prisoners and is transmitted daily into the cells of some 80,000 prisoners, 24 hours a day.