Kate Middleton Is Surprising Londoners Today — by Hiding Her Charity Book Around the City!

Beretta/Sims/Shutterstock

Kate Middleton is stepping out for a good cause.

Early Friday morning, the Duchess of Cambridge stepped out in London to visit the National Portrait Gallery and The Royal Hospital of London to mark the release of her new book, Hold Still: A Portrait of Our Nation in 2020.

For the morning occasion, Kate, 39, was snapped wearing a double wool crepe bright red coat by Eponine, styled over a beige pleated skirt and matching heels. The duchess elegantly paired her look with a beige Demellier mini bag.

According to a Friday release, Hold Still features 100 portraits reflecting the many different faces of individual experiences amid the COVID pandemic. Proceeds from the book raised will be split between leading mental health charity Mind and the National Portrait Gallery.

During Kates’s visit, the National Portrait Gallery also announced that the 100 final Hold Still portraits will become part of their permanent collection.

RELATED: Kate Middleton Corrects Prince William in Their Most Playful Moment Ever — on Their New YouTube Channel!

Beretta/Sims/Shutterstock

Ahead of her morning visits, Kate shared footage from her outing in support of The Book Fairies — a U.K.-based organization with the purpose of sharing books, leaving them in places for people worldwide to discover — in conjunction with the release of her book. The royal took part in hiding 150 copies of Hold Still in secret locations around the U.K., according to the release.

In the post, featuring a video and photos, the mother of three can be seen placing one of her books on the grounds of Kensington Palace.

Get the premiere issue of PEOPLE Royals for glamorous new photos and inside stories royals fans haven’t seen or read elsewhere! Subscribe at peopleroyals.com/launch

Neil Mockford/GC Images

“Let the search begin! We’ve joined @bookfairies_uk for the day to share copies of Hold Still around the UK with you,” the post caption on the Duke and Duchess of Cambridge Instagram page read.

“Each copy is adorned with a gold book fairy sticker, gold ribbon, and has a letter from The Duchess tucked inside. To make this activity even more special, book fairies, the Hold Still judges and participants of the final 100 images are leaving copies at places that gave them hope during the lockdown,” the caption continued.

This special book, launched by the duchess and The National Portrait Gallery, documenting the unique collection of photographs goes on sale today in U.K. bookshops and online.