Attempts to generalise general relativity with the aim of incorporating electromagnetism alongside gravitation began 100 years ago this year. While most of these theories were soon found to be seriously flawed, the approach of Kaluza and Klein has led in recent decades to a wide range of models based on extra spatial dimensions over 4-dimensional spacetime, with a primary aim now being to incorporate the rich properties of the present day Standard Model of particle physics. In this talk we review this background and describe a new approach to unification based on a generalisation of ‘spacetime’ which places the emphasis more upon its ‘temporal’ rather than its ‘spatial’ character, and which is found to lead more directly to the identification of a series of distinctive structures of the Standard Model. While crucially taking advantage of the hindsight afforded by much later developments in the mathematical description of certain symmetries as well as discoveries in the high energy physics laboratory, the simple basis for the new theory can be motivated in a similar spirit as for the earliest attempts at a unified field theory.