In studying space physics, planetary science, and space weather, space-based in situ measurements of the magnetic field are fundamental to understanding underlying physical processes, as well as providing context for other observations. Whilst in many cases instrument design is not severely constrained by the available resource envelope, there are many applications, particularly when using new generations of spacecraft platforms such as CubeSats, that require very low resource sensors. In this context we review the design, development, construction, and flight of the highly miniaturised MAGIC (MAGnetometer from Imperial College) instrument on the RadCube Technology Demonstration CubeSat. MAGIC consists of a boom-mounted (outboard) Anisotropic Magneto-Resistive (AMR) vector sensor connected by harness to a single electronics card inside RadCube. A second inboard AMR vector sensor is mounted on the electronics card. RadCube launched on 17 August 2021 to a sun-synchronous low-Earth polar orbit, with the main mission lasting until April 2022. Routine operations were subsequently extended to the end of 2022, with further special operations in 2023 and 2024 before re-entry on 20 August 2024. Here we review RadCube observations made over more than two years in orbit. Key results from MAGIC on RadCube include meeting ESA space weather magnetic field measurement requirements with both the outboard and inboard sensor, as well as detection of field aligned current signatures at high latitude.