The book is written by Colin McDowell with a foreword by Sienna Miller, and contributions from Anna Wintour, Alexandra Shulman and Diane von Fürstenberg.

The film, titled XV, stars friends of the brand including Sienna Miller, Andrea Riseborough and Poppy Delevingne.

[22] The range is characterised by his signature bold colours and maximalist botanical wallpapers, bedding, cushions, and towels alongside mirrors, lighting, and candles.

[23] The cocktail bar’s decadent interior highlight’s Matthew’s distinct use of pattern and colour through the inclusion of leopard print sofas, gold leaf ceiling hangings, and a 1970s London Zoo cheetah centrepiece.

For this project, he worked closely with UK-based artisans to create a green lounge filled with soft leather furnishings which contrast the building’s otherwise minimalist, industrial aesthetic.

[26] Also in 2023, Williamson collaborated with luxury British footwear and accessories brand, Kurt Geiger, to launch a limited-edition summer collection.

[27][28] This curation of beachwear and furnishings included handbags, deck chairs, shoes, swimwear, and jewellery in a range of bespoke prints created by Williamson.

Matthew is a continuing guest judge[31] on the competition series, offering advice and appraisal to designers looking for their big break.

In 2023, Williamson released a book entitled, Living Bright: Fashioning Colourful Interiors[32][33], published by Thames & Hudson, who describe it as: "A practical guide for how to turn bland corners of your home into a technicolour paradise.