When one Queen meets another: Camilla chats to The Crown's Olivia Colman who congratulates the King's wife on doing a 'great job' during surprise letter reading in London

Queen Camilla delighted audiences at a packed-out literary event in the capital when she made a surprise appearance to read a poignant letter written by the Queen Mother. Camilla, 79, walked out onto the stage at Letters Live at the Royal Festival Hall, an event known for its mystery line-ups of stars who read monologues from real correspondence, to gasps, cheers and deafening applause from the audience. Olivia Colman, who was among the celebrity readers, later congratulated the Queen and told her she 'did a great job' after Camilla admitted she had a bit of stage fright. Speaking in the artists' bar during the interval, the Crown actress, 52, who read three letters during the show, told Camilla: 'You did a great job. I love that they keep it a secret who's coming out. Did you hear the shock when they heard it was you?'The Queen admitted to Elaine Bedell, chief executive of the Southbank Centre, which houses the venue, that she had been 'terrified' before her reading.King Charles's wife, however, looked radiant in a blue Fiona Clare gown as she took her place behind the lectern. She finished her outfit with turquoise and diamond earrings. Speaking to Olivia, Benedict Cumberbatch and his wife Sophie Hunter - who introduced the readers on stage - after the evening's performances, the Queen said: 'All of you were so terrific.'The Sherlock actor told the Queen: 'It's a long walk to that lectern, but once you're there it's a lovely audience.' Queen Camilla delighted audiences at a packed-out literary event in the capital when she made a surprise appearance to read a poignant letter written by the Queen Mother Olivia Colman , who was among the celebrity readers, later congratulated the Queen and told her she 'did a great job' after Camilla admitted she had a bit of stage frightCamilla read a letter from the late Queen Mother to poet Edith Sitwell in which she thanked Ms Sitwell for sending her an anthology of poems to help as she grieved the death of her husband, King George VI.In the note, dated September 15 1952, the Queen Mother, Charles's maternal grandmother, told of how she found solace in the poems as she mourned the King, who had died that February.Camilla, an avid reader who champions the importance of literacy in much of her work, read to the captivated, hundreds-strong audience, saying: 'My dear Miss Sitwell, it was so very kind of you to send me a copy of your lovely book.'It is giving me the greatest pleasure, and I took it out with me, and I started to read it, sitting by the river, and it was a day when one felt engulfed by great black clouds of unhappiness and misery.'I found a sort of peace stealing round my heart as I read such lovely poems and heavenly words.'The letter Camilla read concluded: 'I am deeply touched by your thought of me, I love being given books, and I send you my warmest thanks.'I am yours, very sincerely, Elizabeth R.'Also reading letters were comedians Sara Pascoe and Sindhu Vee, TV barrister Rob Rinder and actors Daniel Kaluuya and Simon Callow, among others. The audience was also treated to performances from rock band Elbow and folk duo The Staves.Sherlock actor Benedict Cumberbatch also met the Queen at last night's performance Sophie Hunter, the wife of Benedict Cumberbatch, introduced the celebrity readers at Letters Live in London Queen Camilla meets with (left to right) Anoushka Shankar, Sara Pascoe, Sindhu Vee, Laurence Fishburne and Dame Harriet Walter during Letters Live, at the Royal Festival Hall, LondonMost of the readers wore wireless headset microphones – and Camilla joked that she was 'upset' that she did not get to wear one.'They didn't dare mic you up maybe,' Sara quipped. The event was held in support of the National Literacy Trust, of which the Queen is patron.Founded in London in 2013, Letters Live has since taken place in New York, Berlin and even at Glastonbury Festival, with recordings of some readings going viral online.It has brought letters written by people as varied as David Bowie and Charlotte Brontë to the stage.Camilla has carried out back-to-back engagements this week after the Royal Family's summer holidays at Balmoral drew to a close amid the Duke and Duchess of Sussex's return to the UK.On Wednesday, she visited the Ebony Riding Club charity in Brixton, south London, after the Royal Mews loaned it one of Queen Elizabeth's beloved fell ponies. Taylor, 17, who escorted Queen Elizabeth and her beloved fell pony Emma on daily outings with her head groom Terry Pendry, is one of two horses that children at the riding school can now enjoy. The black mare moved to Brixton along with a former carriage horse called Margate, known affectionately as Maggie.Maggie, a Cleveland Bay bred at Hampton Court and raised as a carriage horse, worked at the Royal Mews until after the Coronation.An injury meant she was no longer well enough to pull carriages, but after a three-year break she has also been loaned to the charity and the two are now used to teach local children and young people how to ride and care for horses. Keen rider Queen Camilla is patron of the charity and visited yesterday, praising it as 'bigger and better' than ever.'Where are my polos?' she smiled as she was introduced to both animals, stopping to stroke and pat them and offer them the sweets.The Queen was shown inside the centre's stables, where bars separating the horses have been partially removed to allow them to socialise more.The Queen, who wore a white, animal print dress by Fiona Clare, then met year six pupils from Corpus Christi Primary School in Brixton Hill, who have taken part in the centre's schools' programme, learning to ride, groom and muck out stables.Headteacher Jean Connery told her: 'It's wonderful for the children. They would never have the opportunity to do this and it's so good for their confidence. We are very lucky to have this on our doorstep.'The Queen, who opened the current centre 25 years ago, also met volunteers who have helped to create a new community space under a former railway arch at the centre and are training others to volunteer with the horses and community groups.'It's such a lovely place, you must all get so much satisfaction,' she said.Later, Camilla watched as Adam Bentallah, 12, on Taylor, and Isaiah Clayton, 16, on Maggie, gave a riding demonstration in the arena.Afterwards, she presented them both with trophies in recognition of their hard work and dedication.Handing one to Isaiah, she called him a 'star rider' and told Adam his award was 'very well deserved'.There was laughter as dogs nearby began to bark loudly, and she told the schoolboy: 'Even the dogs are applauding you.'She said of the club, which celebrates its 30th anniversary this year, 'It gets bigger and better every time. The first time I came here it was literally a field and a couple of stables.'Jason Hawkes, 17, who has been attending the club as a rider and volunteer for eight years, presented the Queen with a bouquet of flowers.He said afterwards: 'What it's done for me has been unbelievable. It's given me freedom and has opened my eyes to the world. There are so many other things you can do. It's good to get away from city life.'Through access to horses, the charity works to improve the lives of some of the area's most disadvantaged children and young people aged 8 to 18.