Professor Marcel van Herk joined the University of Manchester in 2015 as chair in radiotherapy physics. He has set up a research group focussing on improving the accuracy of radiotherapy currently working on data mining and MR and CBCT based image guidance. He has been active in radiotherapy since 1982. Initially he developed an electronic portal imaging device and its image analysis. As postdoc at Harvard Medical School in 1992, he incorporated 3D image processing, first CT-MR image registration for treatment planning, later measuring organ motion and other uncertainties such as delineation variability. Much of this work has been integrated in the Elekta Synergy cone-beam CT image guidance system developed jointly with Elekta. For the past 10 years, he also held a part-time teaching role as a Professor at the University of Amsterdam working amongst others at the integration of microscopic optical imaging into radiotherapy treatment planning.