An apparatus comprising a processor configured to: receive an input dataset indicative of the amplitude and phase of radar signals received at a plurality of antenna elements, wherein the radar signals have reflected from an unknown number of targets; determine an objective function, based on the input dataset, for evaluation over a plurality of points of a search space, the points of the search space representing possible direction-of-arrival angles of said radar signals from the plurality of targets and wherein evaluation of the objective function is indicative of the correspondence between the possible direction-of-arrival angles of said plurality of targets and the input dataset; evaluate the objective function for a first candidate number of targets K, wherein each target of the first candidate number of targets has a respective first candidate direction-of-arrival angle each corresponding to a point in the search space; perform a first evaluation of a branch metric function based on a second candidate number of targets, K+1, comprising one more target than the first candidate number of targets, wherein the branch metric function is indicative of a change in the objective function between an evaluation of the objective function based on the first candidate number of targets having the first candidate direction-of-arrival angles and an evaluation of the objective function based on the second candidate number of targets, and comprises a function of the respective first candidate direction-of-arrival angles of the first candidate number of targets; and if the branch metric function is greater than a predetermined threshold λ, then the processor is configured to: evaluate the objective function for the second candidate number of targets K+1, wherein the evaluation is based on the first candidate number of targets, K, of the second candidate number of targets, K+1, having the respective first candidate direction-of-arrival angles and the remaining target of the second candidate number of targets, K+1, the remaining target comprising an additional-target having an additional-target-first-candidate direction-of-arrival angle; if the branch metric function is less than the predetermined threshold λ, then the processor is configured to: evaluate the objective function for the first candidate number of targets K, wherein the evaluation is based on at least one of the first candidate number of targets K having a different, second candidate direction-of-arrival angle. receive an input dataset indicative of the amplitude and phase of radar signals received at a plurality of antenna elements, wherein the radar signals have reflected from an unknown number of targets; determine an objective function, based on the input dataset, for evaluation over a plurality of points of a search space, the points of the search space representing possible direction-of-arrival angles of said radar signals from the plurality of targets and wherein evaluation of the objective function is indicative of the correspondence between the possible direction-of-arrival angles of said plurality of targets and the input dataset; evaluate the objective function for a first candidate number of targets K, wherein each target of the first candidate number of targets has a respective first candidate direction-of-arrival angle each corresponding to a point in the search space; perform a first evaluation of a branch metric function based on a second candidate number of targets, K+1, comprising one more target than the first candidate number of targets, wherein the branch metric function is indicative of a change in the objective function between an evaluation of the objective function based on the first candidate number of targets having the first candidate direction-of-arrival angles and an evaluation of the objective function based on the second candidate number of targets, and comprises a function of the respective first candidate direction-of-arrival angles of the first candidate number of targets; and if the branch metric function is greater than a predetermined threshold λ, then the processor is configured to: evaluate the objective function for the second candidate number of targets K+1, wherein the evaluation is based on the first candidate number of targets, K, of the second candidate number of targets, K+1, having the respective first candidate direction-of-arrival angles and the remaining target of the second candidate number of targets, K+1, the remaining target comprising an additional-target having an additional-target-first-candidate direction-of-arrival angle; if the branch metric function is less than the predetermined threshold λ, then the processor is configured to: evaluate the objective function for the first candidate number of targets K, wherein the evaluation is based on at least one of the first candidate number of targets K having a different, second candidate direction-of-arrival angle.