As chief executive of the United Kingdom Atomic Energy Authority, Shah has to oversee the UK’s role in developing fusion energy at Culham, Oxfordshire. As he leaves the post he has held since 2003, the former BP man is confident. “Fusion is a real option for a clean source of energy. We can bring this in within 25 or 30 years. We’re not tinkering with the physics any more.”

The authority, created in 1954 to oversee the atomic energy programme, has gone from bright hopes for the future to a troublesome legacy. One of its main duties now is to decommission research facilities.

The next day Shah flew to one of the most controversial sites, Dounreay, in the north of Scotland, for meetings on safety and security. The prototype fast reactor was shut in 1994, but the clean-up has been hampered by leaks.

Radioactive specks are still being discovered on beaches nearby, even as recently as last month. “I cannot undo accidents which may have happened 25 or 30 years ago,” said Shah, “but I can try to ensure they are not repeated.”

Elsewhere the picture is more promising. Shah, 53, who as one of the public sector’s best paid chief executives earned £277,550 last year, has helped to accelerate decommissioning.

“By the time I leave, 16 of our 26 research reactors will have been fully decommissioned. We are now leading Europe in decommissioning redundant nuclear sites,” he said.

Last year the authority started to bid for decommissioning overseas. “We are now gaining tenders in competition with the best of the private sector, winning more than half the bids we enter,” Shah said.

The following day Shah attended a breakfast meeting with senior figures on the new Harwell Science and Innovation Campus, created on the site of the nuclear research station at the authority’s headquarters. From there to Chatham House, London, to make a speech on energy.

On the Friday, he attended meetings of private- sector companies where he has kept links — the energy company Viridian, which he chairs, and Babcock International (where he is a non-executive director). He closed his week back at Harwell at a reception for local bodies and the public.

Shah is a relatively new phenomenon: a senior figure from industry dipping into the public sector. Now he is returning to the private sector, but he cannot announce his next job.

“I said at the outset that I was a one-term chief executive, and everything had to happen in double-quick time. One of my challenges has been to lead the authority into a more commercial style. I think it helped to have someone like me coming from outside.”

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