  We present a novel derivation of the elastic theory of shells. We use the
language of Geometric algebra, which allows us to express the fundamental laws
in component-free form, thus aiding physical interpretation. It also provides
the tools to express equations in an arbitrary coordinate system, which
enhances their usefulness. The role of moments and angular velocity, and the
apparent use by previous authors of an unphysical angular velocity, has been
clarified through the use of a bivector representation. In the linearised
theory, clarification of previous coordinate conventions which have been the
cause of confusion, is provided, and the introduction of prior strain into the
linearised theory of shells is made possible.
