The article outlines a novel strengthening technique for reinforced concrete beams using external unbonded reinforcement. The advantages of the method lie in speed and simplicity of installation. The article provides a general description of structural behaviour of beams strengthened using the technique, supported by a numerical model to represent the behaviour of strengthened beams. A set of seven laboratory tests on reinforced concrete beams strengthened using the technique are reported, results compared with those of two reference specimens, and the model validated using test data. It is shown that good efficiencies can be achieved when strengthening lightly reinforced beam sections, but that with more heavily reinforced sections only limited strength enhancements are attainable.