I’m going to jump right in and say that this is one of the greatest Christmas picture books of all time: Rosemary Wells is up there with Judith Kerr, Raymond Briggs and Shirley Hughes. Morris’s Disappearing Bag is a funny exploration of family dynamics, using Christmas as an elegant structural device.

The story begins on Christmas morning as Morris and his three siblings tear their presents open.

‘Morris’s brother, Victor, got a Hockey outfit.

‘Morris’s sister, Rose, got a beauty kit.’

So far so 1975. But turn the page and we discover signs of a more progressive household as Morris’s other sister Betty opens her chemistry set. The traditional roles are soon blurred altogether as the elder siblings swap presents and begin a voyage of self-discovery and gender experimentation. This is the 70s after all.

‘Victor made himself beautiful and Betty played goalie and Rose invented a new gas.’

All except poor Morris, the baby whose new teddy bear is of no interest to anyone. Feeling left out he gets the hump and even refuses to eat the fine Christmas dinner (of carrot soup thankfully). Nobody is sure why.

‘It was the gas,’ said Betty. ‘He breathed it in.’

Then Morris discovers an unopened present and things take a turn for the strange. It contains a magical disappearing bag and once hidden inside he is able to amaze his siblings and amuse the eagle eyed reader.

After Morris reveals himself, his brothers and sisters all disappear inside the bag, giving him free rein over their presents. Any youngest child’s Christmas dream.

Radical sixties picture book pioneers Maurice Sendak and Tomi Ungerer are definitely an influence, both on Wells’s art and her honest exploration of Morris’s feelings. She describes her work as non-fiction, basing characters and situations on her own family and upbringing. As a result every piece of dialogue and every look and expression feels real.

Rosemary Wells worked as a picture book designer before becoming a prolific author and she clearly took those early skills and put them to use in her books. The action moves between split frames seamlessly and the double page spreads are packed with information yet never feel overcrowded.

For reasons unknown, Wells re-illustrated the book in the late 1990s, adding far bolder colour and more detailed backgrounds. The family home appears to have enjoyed an upgrade but pleasingly its leporine inhabitants remain stubbornly old-fashioned. Morris’s mother has switched one blowsy dresses for another and his father changed from an overgrown Peter Rabbit ensemble to a used car-dealer at the country club look. That sofa though.

The perfect Christmas book then and one that achieves the impossible feat of being perfectly readable at any time of the year.