The Mega Amp Spherical Tokamak (MAST) is the centre piece of the UK fusion research programme.In 2010, a MAST Upgrade programme was initiated with three primary objectives, to contribute to: (1)testing reactor concepts (in particular exhaust solutions via a flexible divertor allowing Super-X and otherextended leg configurations); (2) adding to the knowledge base for ITER (by addressing important plasmaphysics questions and developing predictive models to help optimise ITER performance of ITER) and (3)exploring the feasibility of using a spherical tokamak as the basis for a fusion Component Test Facility.With the project mid-way through its construction phase, progress will be reported on a number ofthe critical subsystems. This will include manufacture and assembly of the coils, armour and supportstructures that make up the new divertors, construction of the new set coils that make up the centrecolumn, installation of the new power supplies for powering the divertor coils and enhanced TF coilset, progress in delivering the upgraded diagnostic capability, the modification and upgrading of theNBI heating systems and the complete overhaul of the machine control infrastructure, including a newcontrol room with full remote participation facilities.