'A Letter in Mind' sees over 500 artists specially customise the humble envelope

The artworks use a simple envelope as a starting point, while the concept uses the same main hook of Secret 7" in that each artist behind each piece remains anonymous until their work is sold.

Proceeds from sales will go towards helping people with neurological conditions and supporting vital projects at The National Hospital for Neurology and Neurosurgery, where staff have been working under enormous pressure responding to the Covid-19 crisis.

The theme for this year's exhibition, now in its seventh year, is 'Everyday Things', reflecting on how life has become simpler during lockdown. Other artists taking part include Gill Rocca, Harry Pye and Mark Entwisle; illustrators Tim Hopgood, Polly Dunbar and Bethan Woollvin; architects Laurie Chetwood, Amin Taha and Andrew Grant; actors Kevin Eldon, Sophie Thompson, Joanna David and Phyllida Law.

Dame Zandra Rhodes, fashion designer and founder of the Fashion and Textile Museum, is taking part for the first time, saying: "I found lockdown very peaceful. I had space to think which was nice. It also meant I had time to create an artwork for A Letter in Mind; it is such a lovely idea, creating art on an envelope."

Dame Zandra continued: "It is a great idea as a fundraiser. I like how it is pot luck for people buying artworks as they are anonymous during the exhibition. You can get something because you like it. It is very democratic for all the artists involved too."

Two regular contributors to A Letter in Mind are 1995 National Portrait Gallery's BP Portrait Award winner Ishbel Myerscough and her sister, award-winning artist and designer Morag Myerscough.

Ishbel Myerscough said: "It is great that the exhibition is anonymous, guessing whose it is, makes it more fun! If an artist doesn’t put a name on a piece, they can’t rely on their signature to sell it. They have to work harder."

"I love the idea of having something precious created on a throwaway thing like an envelope for just £85. We always doodled on envelopes as children. My mother, if she saw a bird or a cat through the window, would find the nearest thing on the kitchen table to draw them on, usually an envelope. When we were on the bus, she would give us one out of her bag for us to draw on. I still have them in my handbag for the same reason."

Morag Myerscough, whose installation 'A New Now' will be in Paris until December, said: "Displaying and selling the artworks anonymously is definitely part of the appeal. People can choose something they want and are giving to charity in the process. You want your piece to be anonymously desirable!"

She added: "It is a good way for artists to feel they can give something, especially at the moment. If you are not working on the front line, you can help with your abilities. Coronavirus and lockdown have shown us that people love crafts and drawing. People are desperate to do creative things. Connecting art to health is essential."

Artist and portrait painter, Mark Entwisle, took part for the first time in 2019, shortly after having treatment for a brain tumour at the hospital the charity fundraises for.

"I am delighted to take part," he said. "I have direct experience of what The National Hospital can do for patients. I feel so grateful for how they helped me and also for everything they, and all NHS staff, have been doing to help patients during the Covid-19 crisis. Taking part in A Letter in Mind was such a perfect way for me to show my gratitude."

The National Brain Appeal's A Letter in Mind – Everyday Things runs from 5 to 8 November, 11am until 6pm, at gallery@oxo, Oxo Tower Wharf, London, and can be previewed online and at aletterinmind.org from 11am on Wednesday 4 November. Sales will take place online only from the next day at 11am.

Admission to the show is free, with information about how to book and buy artworks at aletterinmind.org.