Her best-known work is The Twelve and the Genii, a low fantasy children's novel published by Faber in 1962, for which she won the 1962 Carnegie Medal, the Lewis Carroll Shelf Award, and the 1968 Deutscher Jugendliteraturpreis.
The Pekinese Princess (1948), Clarke's first book, is a long-ago fantasy of talking animals and trees in a fairy tale Chinese setting, a human-like world without humans.
During their train trip they coincidentally meet a boastful young man who tells them he is a dealer in second-hand jewellery, and shows them a strange gold item.
The children work to untangle a mystery which includes secret and illegal archaeological digging, theft of historical artefacts, and even the haunting by the ghost of the Celtic smith who buried the hoard and died in tribal warfare.
This commemorates a bitter defeat at Maldon in Essex by Danish raiders in 991, led by a Viking called Anlaf, who is possibly Olaf Tryggvason, later the king of Norway, and himself a character in the Icelandic Heimskringla Saga.
She won the annual Carnegie Medal from the Library Association, recognising The Twelve as the year's best children's book by a British subject,[6] and the German Kinderbuchpreis.
Visiting Italy with their parents, while their father attends a historians' conference, Rufus and Drusilla set free the ancient god-satyr Silenus, and his enemy Medusa.
She soon finds herself as part of the office-based Intelligence team analysing the multitude of reports from secret agents and Resistance workers and spies in Europe, warning of the dangers of the anticipated German revenge weapon, the V1 “buzz bomb” or “doodlebug”.
Frequently, and diversely, the characters quote, mention, or allude to a wide range of authors, literature, music, history, and culture, including Dickens, Tolstoy, Mozart, Bach, Ibsen, Shakespeare, Tennyson, Freud, Plato, Jung, Locke, Bunyan, Lewis Carroll, Dylan Thomas, Sassoon, Coleridge.
Lewis (when his wartime writing and radio talks on Christianity were popular, but before he became a best-seller children's fantasy author), Benjamin Britten and Peter Pears, the “Punch” cartoonist and patriotic war-poster artist Fougasse.
The novel is threaded through with quotations and references to Egyptian mythology, notably Thoth, the ibis-headed god of knowledge, truth and justice, as well as the Metaphysical poet Thomas Traherne, and the Renaissance renegade monk Giordano Bruno, and the Hermetic writings, along with many other literary, musical, and artistic motifs.