Introduction

Our aim is to perform precision tests of gravitation in the laboratory or in space. We have spent a number of years developing a new device for measuring weak forces: the Spherical Superconducting Torsion Balance (SSTB) plays a central role in our experimental programme. We are currently completing a search for new time reversal violating forces using the first SSTB. Such an interaction would generate a force between intrinsic spin and matter and would be mediated by an axion-like particle. Development of the second generation of Mk2 SSTB is well underway. We intend to use the new device as a detector in a precision determination of the Casimir force. This work is funded by BAE Systems and the Engineering and Physical Sciences Research Council. We are also planning a test of the inverse square law of gravitation at short ranges. This work is funded by the Leverhulme trust and Particle and Astronomy Research Council.

In collaboration with Prof T.J. Quinn FRS of BIPM (International Bureau of Weights and Measures) we have performed a precision determination of Newton's constant of gravitation. This work is on-going and exploits the remarkable properties of the torsion strip balance. This is another new instrument in experimental gravity and was developed over a number of years at BIPM. We have been working on the joint NASA/ESA project STEP for a number of years. This is a mission aimed at testing the Weak Principle of Equivalence using a drag-free spacecraft.