If the attractive, hand-painted invitation is anything to go by, the coronation will be a neo-pagan rite in which King Charles III is invested as Archdruid, Master of the Hobby-Horse and Lord of Summer Isle. That’s because the most prominent image in the intricate, joyous floral design – by heraldry artist Andrew Jamieson – is the wryly smiling face of the Green Man. This emerald visage, the standout feature in Jamieson’s elegantly swarming design, belongs to an ancient, pre-Christian divinity who can still be seen in the architecture of British medieval churches, a leafy mug among all the gargoyles. The face of a fertility cult that existed at the margins of Christianity fits perfectly into Jamieson’s loving recreation of the playful natural imagery that is found in medieval art. In manuscripts from the era, the main text is usually religious and orthodox, while fun and fantasy are given free rein around the margins. Here, the official message of the invitation occupies a central empty square, while the Green Man and his ever-renewing natural kingdom sprawl around the edge in living colour. Is this cheeky chappy a benign image of Charles III, the environmentalist king? The artist seems to recognise the monarch’s love of horticulture and his warnings about humanity’s despoliation of nature in his luscious interweaving of bluebells, dog roses, strawberries, a wren and a robin, not to mention cornflowers, a butterfly and other delights of the British countryside. But that starring role for the Green Man seems to be a clear summons for Shakespearean sprites to bring some subversive May fun to the coronation. Recipients are invited “to be present at the Abbey Church of Westminster” for the Christian ritual that has conferred (divinely sanctioned) authority on monarchs since the dark ages. We haven’t had a coronation for a while, so the reality of this ceremony may come as a shock: it is the only surviving example of a practice that appeared in early medieval Europe when the church was imposing its authority on new feudal overlords called “kings” and rewarding them with religious sanction for their power. The central moment of the coronation is the new monarch being anointed with holy oil. The chrism oil that will be used to anoint King Charles was blessed last month in the Church of the Holy Sepulchre in Jerusalem, by his beatitude patriarch Theophilos III and the most reverend Hosam Naoum. That’s quite a lot of ceremony already: the coronation of a British monarch, clearly, is as venerable a religious moment as the election of a pope. On the invitation, however, religious ritual is transformed into something wild and Puckish: the marginalia have taken over the Abbey. The Green Man seems to be cheekily licencing another kind of coronation, one that is deconsecrated, even pagan. Jamieson, who has previously designed coats of arms for clients including the late Colin Powell, former US secretary of state, was selected from eight members of the Art Workers’ Guild. His choice suggests that Charles wants to be our pagan patriarch as well as God’s Anointed. Is he the Greene King? Perhaps this is a message not to take the pomp of the Abbey too seriously. The new monarch has already set out to be a religiously plural figure, visiting different religious communities to make good on a stated wish to be defender of “faiths”. This invite suggests that this also includes neo-pagans, witches and followers of the old ways. However you read its springtime symbolism, the coronation invitation is a witty, skilled performance that speaks well of King Charles III’s feel for art and sense of humour, as well as Jamieson’s talent. Now all we need is a maypole outside Westminster Abbey.