[en] An account is given of the beginning of fusion research at Harwell following early experiments at the Clarendon Laboratory and Imperial College, and which from 1948 became the Official Programme under the Atomic Energy Technical Committee. A significant event was the publication of the Lawson criteria in 1955. The design and construction of the ZETA device and the early experimental results are discussed. A new site at Culham was selected for all fusion work, and a new experiment to be known as the Intermediate Current Stability Experiment (ICSE) was proposed. Owing to budgetary constraints ICSE was cancelled in 1960. (U.K.)