The document discusses proton beam radiotherapy and its advantages over traditional x-ray radiotherapy. It describes the equipment used for proton beam therapy including cyclotrons, treatment rooms with rotating gantries, patient immobilization devices, and beam shaping components. It also compares treatment plans using proton therapy to those using intensity-modulated x-ray therapy, showing that protons can lower doses to surrounding healthy tissues. The case for developing a proton therapy facility at University College Hospital in London is made due to its location in a center of medical expertise and research.