ZETA was an early attempt at a fusion reactor. Neutrons were observed coming from the hot plasma, and it was assumed that they were the result of fusion, although there were other possible causes.
The issue came to be something of a cause célèbre, since the British government had agreed to synchronise the release of results with the Americans. The delay led to allegations in the British press that the Americans were trying to suppress the British success so that they might catch up.
Although no official announcement had been made, the press were very much aware that Harwell thought that it had achieved a successful fusion reaction. Eventually, a full-scale press conference was held at Harwell in January 1958, including a large contingent from overseas and an outside broadcast unit from the BBC – very much a novelty. In those days, there was no media training, and Sir John Cockroft was unwisely pushed into saying that he was almost certain that fusion had occurred.
Later experiments with ZETA showed that in fact the neutrons had not been the result of fusion, and the reputation of Harwell and Cockroft suffered as a consequence of the announcement of the failure.
Opposite is shown a copy of the letter written to Cockroft by BBC television. The use of the word 'triumph' is indicative of press reaction at the time.
An article by Sir John Cockcoft in New Scientist dated 30 January 1958.
BBC article on ZETA.