Multi anvil presses (MAPS) are used worldwide for high p/t work. The 'Walker cell' has made maps more accessible for earth sciences research. A Walker cell is installed at Daresbury allowing X-ray diffraction data to be obtained at high p/t simultaneously. Its 'inventor', Prof D. Walker, is visiting Daresbury and Manchester for 1 year from October, 1997, and he is working with the PI's in developing the equipment so that higher p will be attainable, with better controlled and calibrated t. In situ experiments will provide data on the molar volumes of garnets and CO2 as a function of p and t. The results will improve thermodynamic databases allowing relevant mantle mineral reactions to be calculated more robustly.