This paper provides a technical description of the neutron emission profile monitor as used routinely at the Joint European Torus (JET), and includes representative examples of its operational capabilities. The primary function of this instrument is to measure the neutron emission as a function of both position and time in a poloidal section through the torus. For the first time, sawteeth and their associated reversals have been observed using a neutron diagnostic. Comparison with other JET neutron diagnostics indicates agreement, in terms of absolute neutron emission rates, to within ±15%. This was the first such instrument routinely in use on any tokamak. It provides unique data which are independent of all other diagnostic measurements.