During 1997, JET carried out a campaign of operation in deuterium/tritium. A total of 99 grams of tritium was admitted to the torus using gas puffing and neutral beam injection. With a site inventory of 20 grams of tritium, this required repeated re-processing of the gas recovered from the torus using the JET active gas handling plant. Around 220 tokamak pulses were carried out with tritium concentrations above 40%, during which a total of 2.5.1020 14 MeV neutrons were produced. Emphasis was placed on re-producing conditions close to those anticipated in the ITER experimental fusion reactor, in particular maintaining dimensionless parameters important in the physics of confinement. The experimental program included high fusion yield hot-ion and optimized shear scenarios in particular for the study of alpha particle physics. Achievements included a maximum fusion power of 16MW in hot-ion H-mode at a Q of 0.6; first production of DT power (8MW) in optimized shear; a Q of 0.2 for 5 seconds in an ITER relevant steady state ELMy H-mode at a fusion power of 4MW; a Q of 0.22 in RF only discharges; and observation of alpha particle heating. Tritium was found to give a marked reduction in the Hmode threshold and an improvement in edge pedestal stability but no change in global confinement. The optimized shear scenario required re-optimization in tritium, only partially achieved. The results are generally consistent with ignition in ITER. Retention of tritium in the torus is much higher than anticipated and tritium recovery during the clean-up campaign was modest. The divertor tiles have since been replaced remotely with no personnel access to the torus. Tritium release and the dose to personnel have been well within the low approved levels. JET has successfully completed this tritium campaign, producing both physics and technical data invaluable to the design of next step devices. The results in particular demonstrate the importance of operations in tritium in reliably predicting the performance of future machines.