The performance of a fast thermal response miniature Adiabatic Demagnetisation Refrigerator (ADR) is presented. The miniature ADR is comprised of a fast thermal response Chromium Potassium Alum (CPA) salt pill, two superconducting magnets and unconventionally, a single crystal tungsten magnetoresistive (MR) heat switch. The development of this ADR is a result of the ongoing development of a continuously operating millikelvin cryocooler (mKCC), which will use only magnetoresistive heat switches. The design and performance of the MR heat switch developed for the mKCC and used in the miniature ADR is presented in this paper; the heat switch has a measured Residual Resistivity Ratio of 32,000±3000 and an estimated switching ratio (on thermal conductivity divided by the off thermal conductivity) of 15,200 at 3.6K and 38,800 at 0.2K when using a 3T magnetic field. The performance of the miniature ADR operating from a 3.6K bath is presented, demonstrating that a complete cycle (magnetisation, cooling to the bath and demagnetisation) can be accomplished in 82s. A magnet current step test, conducted when the ADR is cold and fully demagnetised, has shown the thermal response of the ADR to be sub-second. The measured hold times of the ADR with just parasitic heat load are given, ranging from 3min at 0.2K with 13.14μW of parasitics, to 924min at 3K with 4.55μW of parasitics. The cooling power has been measured for operating temperatures in the range 0.25–3K by applying an additional heat load to the ADR via a heater, in order to reduce the hold time to 3min (i.e. approximately double the recycle time); the maximum cooling power of the miniature ADR (in addition to parasitic load) when operating at 250mK is 20μW, which increases to 45μW at 300mK and continues to increase linearly to nearly 1.1mW at 3K. To conclude, the predicted performance of a tandem continuous ADR utilising two of the miniature ADRs is presented.