‘A letter is a private thing,” says Sanjeev Bhaskar. “When you’re reading a letter, you hear the other person’s private voice. So, if you read it out loud, you’re speaking in their voice, their private voice. But if you’re reading it in front of an audience, it’s for the audience, too. So the whole thing is both public and private. It’s not as simple as you think.”

Welcome to Letters Live! Well, welcome to backstage at Letters Live at the Royal Albert Hall. We’re in the Artists’ Bar in the basement, where various famous people, mostly actors, are preparing to read out letters – some funny, some touching – in front of an audience of 5,000 people. Tonight is the 10th anniversary of Letters Live, a birthday celebration. There’s a table with nibbles, a bar with cocktails and the vibe is friendly and collaborative, with people saying hi to old friends, introducing themselves to others. In the corner, there’s an artist drawing pictures; someone from a whisky company is offering engraved bottles to the celebrities for them to take home. Everything, and everyone, seems relaxed.

Still, as Bhaskar points out, the actors’ job tonight is not as simple as it might seem. I’d insisted it was a doddle, surely: no learning of lines, no cameras, no walking and talking. Just stand in front of a lectern and read a great letter out loud. “No, you have to think about it,” he says. “You want to do the letter justice. You can’t not do the prep.”

No surprise, then, that on closer inspection, the actors appear to be in varied states of nervous excitement. Stephen Fry seems fine, chatting easily at a table with the creator of Letters Live, Jamie Byng. On a sofa, Gillian Anderson, solo, cool and queenly, is quietly reading her script on her phone with her AirPods in. Opposite her is activist Harnaam Kaur, who is excited. It’s her first time at Letters Live and she’ll be reading her own letter, which she wrote to her younger self. But, “I had an operation four days ago,” she says. “If I actually die on stage, I hope people realise I tried, so they don’t feel like they wasted £20.”

Will Sharpe, from The White Lotus, is friendly, a little tense. Vivian “Rye Lane” Oparah, charming, introduces herself. And here comes Minnie Driver, a dynamo of charisma and cheekiness. “I was feeling fine about this,” she says. “But I’ve just seen Ben [Benedict Cumberbatch] and he said he was nervous and now I’m not so sure.”

Rob “Catastrophe” Delaney seems happy enough.

“I’ve got a good letter to read,” he says. “It’s kind of self-righteous. One time I wrote a letter after a girl broke up with me. That was quite self-righteous, too, a screed, like, I’m gonna show you why you shouldn’t have dumped me, by being a psycho. And then I read it and I realised, I don’t need to send that, and I threw it away and I felt better immediately. Who are those kinds of letters for? They’re for you, really. You write it, you read it, great, goodbye.”

With all these famous people, the appeal of the evening might seem to be just that – 15 celebrities in a night. Bargain! – but it’s not. It’s the letters. There’s something about a well-written letter that makes Letters Live more of an emotional rollercoaster than you might expect. Evenings swing between riotously funny and devastatingly moving, the tears helped by appropriate music performances. A few years ago, I went to a Letters Live in Brixton prison – the 30th one – where Kae Tempest performed part of their work Brand New Ancients. Afterwards, Olivia Colman, who was there to read Leonard Cohen’s final letter to Marianne, was in complete pieces.

So there is a pressure on the performers to hold it together, to do the work. And, onstage, there’s not much time for them to do it. The letters are short, some just a few lines long. Every word has to land, each phrase.

I nip to the loo and see Benedict Cumberbatch, away from the rest of the actors, leaning against a wall, reading his script. Minnie’s right. He looks nervous.

When was the last time you wrote a letter? Let alone one you might want to read out loud? These days, we spend a lot of time writing – texting, WhatsApping, emailing, composing social media posts – but it’s rare we bother to pick up a pen and paper, or even print out something we’ve written. And perhaps because we write (type?) so often, so casually, we value it less. We bang out our half-thought through theories, our silly quips, our hot responses. Our fingers flick over keyboards and phones, writing, writing, and then we look away as all our words just… disappear. Nothing remains, unless you’ve got the screen shot, unless you wangle the paper into the printer and get a real-life copy.

Letters – more careful, more permanent – last longer. They have significance. They require composition, editing, thought, some crossing out and starting again. (Mark Twain once wrote to a friend: “I apologise for such a long letter, I didn’t have time to write a short one.”) And letters have form. Some of us remember English lessons where we learned how to write them. How to set out a letter correctly, how to address an envelope, which signoff to use with “Dear Sir/Madam” (yours faithfully), which with “Dear Mrs Bloggs” (yours sincerely). We remember the fuss about buying stamps, licking the envelope, traipsing to the pillar box. And we still keep letters: from our parents, our grandparents, our children, our friends. Actual physical items, created for us in a particular moment. Like photos, but, these days, more personal.

The other day, I was clearing out my office and, underneath piles of my children’s old school books, I found a plastic box. I’d slung a lot of significant correspondence in there and among it all I found three letters and a torn-out advert. The ad was from 1988, looking for a pop writer for Smash Hits magazine. I was not qualified for the job. But my letter of application, which I wrote out neatly and then copied on to a friend’s Amstrad computer (the first time I’d ever used one), was written in extreme Smash Hits style, full of jokes and inverted commas. The other two letters were from Barry McIlheney, the magazine’s editor, asking me to come in for an interview and offering me a few days’ work. Those letters changed my life completely.

I took photos of the advert and letters and put them up on Instagram, where they got a big reaction, partly because they’re old, but also because they’re artefacts; physical items, unique. Not a virtual response, a standard email that can be sent to thousands of strangers, with one click. Precious.

In another box, I found funny letters from friends I don’t see any more, from my brother when I left home. One from my dad, who never wrote much. It’s just a few lines about a David Hockney exhibition, but my dad is now elderly, with Alzheimer’s, and he can’t write properly or control his thinking enough to come up with a fully realised written sentence. So that letter is important, too. But not for Instagram.

Back in the green room at the Albert Hall, more people are arriving. Olivia Colman, bundled in a big scarf, is laughing with Jodie Whittaker. Colman is a Letters Live veteran, Whittaker a newbie. Whittaker’s energy is always fizzy, but tonight she’s electric, buzzing with excitement. “I’ve never done this before!” she says. “Arrgh!” Colman’s warmth melts the ice of Gillian Anderson, who joins her, Driver and Louise Brealey, the naughty girl crew.

I sit with Stephen Fry, avuncular and erudite. The inventor of the pillar box, says Fry, was the novelist Anthony Trollope, who used to work for the Post Office. Before his invention, the father of a household could frank a letter, which cost money (unless they were an MP or an aristocrat). Then the Penny Post was introduced and you’d send your servant to a Post Office or go yourself and present your letter to be posted. Trollope had the idea of putting post boxes on corners. “The odd thing was,” says Fry, “that it had an effect he had never imagined. It allowed women a new source of independence. For the first time, they could write a letter and personally post it. They didn’t have to trust a maid, who might report to their father, and they didn’t have to get permission from their father. So they could write to their beloved, like Robert Browning and Elizabeth Barrett. They could conduct love affairs in letters.”

Back in my office, I find little notes from my children. One says: “I hate writing, bcas I thing it is bawing. I love football.” Another: “To mum I’m sorry. Plees do you fgiv me.” When they were young, the kids slipped letters under my bedroom door. The process of their writing the notes in private and then delivering them formed part of something they wanted me to know was important.

The significance of letters increases with each stage of the process. The writing, the sending. If you send a letter by post, there are a few days when it exists, but it doesn’t (Schrödinger’s postcard). It’s not there, but you know it’s been sent. It hangs around in your mind, both a fact and an imagining.

On stage, the performers move swiftly on and off. The more famous get oohs from the crowd as they walk on. Bhaskar reads a Spike Milligan letter that makes me howl. Delaney’s, from Pliny the Younger to Septicius Clarus, is funny, too. Driver reads a lengthy, hilarious viral complaint letter from Hannah Scorer to Boots about the extreme inefficacy of their hair-removal wax strips, which reminds me that some letters are written for others to see. Kae Tempest ends the show with their song, People’s Faces. Afterwards, they tell me they felt overwhelmed. “I’ve been in a room writing on my own for the past few weeks.” The letters made them cry.

They made me cry, too. It’s the reading out of them, the public acknowledgment. Small songs from people who don’t sing. A private thought told to a friend. Something so significant you have to write it down, send it away, on a journey to someone who you need to see it, to read it and understand. To keep.

Stamp of approval

A letter can change a life – even if it’s never sent

Vivian Oparah I was in LA with my best friend and I was trying to make it to a screening of Rye Lane, but I couldn’t get there. But he did and he watched it and wrote me a letter straight after watching it and then gave me the letter. It was the sweetest thing. We’ve known each other for a very long time and he just captured the immediate feeling of, I guess, pride. I’ll keep the details close to my heart. I’ve kept the letter, of course! It’s in my dream journal.

Harnaan Kaur A letter that I’m scared to write is to the love of my life. You know that phrase, the one that got away? He was the one who got away. Since I was 18, I’ve known him, and I’m 33 this month and he’s just one person that I’ve never gotten over. And he knows that! Of course, he knows. I should write him the letter really.

Minnie Driver The last text I have from my mum is: “Have a good weekend, darling, admire the infinite sky.” I don’t think she knew she was going to die, but I love that that’s the last letter I got from her. It’s not a letter, but it’s written. To be honest, I would have loved it if her last text had been: “Buy beans, bread, frozen chips.” But to have that as her last, it’s such a beautiful thing.

Will Sharpe I got into trouble for something and I wrote a letter of apology, and I remember I was told that the letter was a good letter of apology, but that I was still in trouble. Despite my brilliant letter, it didn’t work. I was still punished.

Rob Delaney My wife and I dated long distance for the first year of our relationship, so letters were really important to us and those I treasure. I also recently found a postcard that I had written to my dad but didn’t send. My dad died, and I have this letter, just about stuff my kids were up to when we went to the Lake District that I think he would have enjoyed. I’m glad I have it.

Sanjeev Bhaskar There was a girl that gave me a hard time when I was at university and I concocted a quite fantastical revenge that involved fake letters from France. It was all about a job. The letters would require her to go to France and she would go there and find out that there was no job. I really constructed these letters, I was going to make letterheads and get someone I knew who lived in Paris to post the letters from Paris. I wrote this whole plan out, about four pages and looked at it and thought, I think this might work… And that was the moment that I decided not to send the letter.

Jodie Whittaker When my grandma died my dad’s mum, we were going through her stuff, and she was an absolute hoarder, there was so much of it. But we found this letter from an ex-husband we didn’t know existed, begging her to come back. In the early 40s, during the second world war. He wrote this beautiful letter, saying this is why he loved her and he wanted her back. But she was with my grandad up north!

Stephen Fry I had rather a tricksy adolescence, and ended up in prison. It seemed like any hope for my future was blasted. I scrambled to my feet after being released and tried to get some A-levels, which I’d missed due to being expelled from so many schools. And I took the Cambridge Entrance exam too, by going to the local library and getting out past papers, and I paid to be invigilated myself. Every day after the exam, I would wait for the post, which came at about 11 in the morning, to see if I’d got into Cambridge. But, nothing. So one day, I could bear it no longer and I said to my mother, “I’m going into Norwich to see some friends, I can’t just wait for the post again, nothing’s coming, it’s obvious I haven’t got in”. And I went to the place for the young and bohemian of Norwich, which was called Just John

Tickets for Letters Live’s next show, 6 March 2024, are available at letterslive.com. Keep up to date with all upcoming show information by joining the mailing list, including the New York spring 2024 show to be announced soon.