1. A method of predicting output values ŷ of a physical system from a set of measured inputs r j of the system, wherein at each time t when a prediction is made, the method comprises the following steps: (a) storing the set of measured inputs r j (t i ) and the corresponding measured output y(t i ) at each of a predetermined number n of times t 1. .. t n earlier than t; (b) initializing a model of the system, which generates a predicted output ŷ(t) from the set of measurements r j (t), to a predetermined initial model; (c) using each of the predetermined number n of sets of measured inputs r j (t i ) and output y(t i ) to adapt the model; and (d) using the adapted model to predict the output value ŷ(t) of the system at time t from the set of measured inputs r j (t) of the system at time t.