The transmission-line matrix (TLM) method is a space and time discretising method for computation of electromagnetic fields. It is based on the analogy between the electromagnetic field and a mesh of transmission lines. The TLM method allows the computation of complex three-dimensional electromagnetic structures and has proven to be one of the most powerful time-domain methods along with the finite difference time domain (FDTD) method. The TLM was first explored by Raymond Beurle while working at English Electric Valve Company in Chelmsford. After he had been appointed professor of electrical engineering at the University of Nottingham in 1963 he jointly authored an article, "Numerical solution of 2-dimensional scattering problems using a transmission-line matrix", with Peter B. Johns in 1971.