In 1997, Brian Clarke submitted a proposal for stained glass windows for Heiliggeist-Kirche, one of the few remaining Gothic churches in Germany, here located in Heidelberg.

In the exhibition catalogue Brian Clarke–Linda McCartney: Collaborations (1997), Stefan Trümpler, director of the Musée Suisse du Vitrail, Romont, writes of this unrealised project:

‘Clarke developed a design that links modernity and ancient craftsmanship by using a different single ornamental element, invented by medieval stained glass painters, in each window. This ornament is transformed into a regular, precise pattern by virtue of a computer-generated repetition. Each ornament originates from another European country. To give an example: the 'fleur de lys', a stylised clove, was first used on a larger scale in the stained glass of Sainte-Chapelle in Paris.

These formerly modest, almost hidden elements of a figurative composition are retrieved from anonymity and become the foundation of an exuberant and abstract composition. This abstraction is modified and at the same time enhanced by scriptural elements, enlarged details of manuscripts chosen for compositional (the beauty of the abstract gestures of calligraphy) and historical reasons. The history of those texts used in the designs connect them with the church's location as they have been taken out of the 15th century manuscripts first recorded and formerly owned by the Biblioteca Palatina, one of the most famous libraries of ancient times. This library had been situated inside the church, where Brian Clarke's designs are intended to echo a culture that has been at the very heart of the history of this building.

This project is an outstanding example of Clarke's ability to tune in to an architectural situation that demands not only a subtle consciousness of history, but also an aesthetical idiosyncracy that can keep designs for a 14th century building cautiously suspended between historical reminiscence and modernism.’