What's it like being an ex-chief scientific adviser to a major western government who is keen to influence the debate but is no longer on the inside track? Professor Sir David King is in that position. He spoke today at Hay.
Not many clues emerged, but King confirmed his reputation as an instinctively frank man inclined to speak out, as he did against Washington's myopic policies towards climate change and in favour of nuclear power.
In a peroration new to me, the man who was Tony Blair's science man in No 10 for seven years (2000-2007) argued that Britain already has so much uranium waste stored at Sellafield that it could run a nuclear programme equal to France's for 100 years - "without importing a single gram".
If it's not going to be treated as fuel, it has to be treated as the worst kind of waste. Let's do it, was the message: the climate change crisis is too urgent not to act on this vital low-carbon option. Fifty years' worth will only add 10% to our stock of waste.
Even I know this is a controversial message. Critics like George Monbiot have been addressing similar, polite but inquiring Hay audiences in the same sodden Welsh field this week. Yet King's audience took it calmly. And his co-author, journalist and TV presenter Dr Gabrielle Walker, was positively supportive.
No surprise there, I suppose. They could hardly have had such a basic disagreement and have written "Hot Topic: How to Tackle Global Warming and Still Keep the Lights On". On stage this was also an evidently effective partnership, with mutual parity of esteem between old bloke (68) and telegenic blonde. She calls him Dave.
It was Dr Walker who set the scene: your average UK citizen's carbon footprint is 11 tonnes (the EU average), in the US it's 27 tonnes, India 2.2 tonnes - precisely the level to which we must aspire to meet Gordon Brown's declared ambitions.
They can spend $3 trillion on a war which didn't solve terrorism, but can't spend mere billions addressing climate change technology, said the man who set up the £1bn Energy Technologies Institute, which provides seed corn money to promote such ventures. It seems the private sector is now moving faster than governments.
How do we influence governments? King recalled getting the cabinet to back the policy which resulted in the 2003 energy white paper. Then it was thought enough that the old Department for Trade and Industry's energy group should draw up plans.
But in a country where 50% of energy is consumed by the built environment and another 30% by road transport (global aircraft take 1.7%, stand-by buttons on equipment a startling 1%), it needs action by all government departments, by private commerce and by individuals, plus global action. That's what the 2007 white paper managed to say.
Slow progress, but King, who now heads the Smith School to tackle such issues at Oxford, sounds like an optimist even as he says that we have little time to get it right. Even the cyclical 10-year cooling of the Gulf Stream - due about now - risks boosting public complacency in northern Europe because it will offset the effects of global warming. Of course then the cycle and the underlying trend will hot things up again ...
Market solutions can work brilliantly, but only in certain settings. King is a champion of carbon trading schemes which he says must become global - and punitive. Together with the search for ways to farm solar power, plus carbon capture and storage, this is the most pressing of current priorities.
But other activities need stimulus and regulation, too. Why not just ban tungsten filament bulbs - and do it now? Why not force new buildings to have photovoltaic roofs, photovoltaic exterior paint even? Why not chivvy consumers so they no longer admire gas guzzlers? It seems heavy energy-burning remains a high-status activity.
Public opinion is also a vital part of the political pressure. "Beware of politicians who make brilliant speeches and then do nothing about it," King warned. Voters must examine the follow-through. Tony, can he be talking about you? Dr Walker, who chips in throughout with her own perspectives, says that every new technology needs a champion. Carbon capture's champion seems to be the oil companies: can we trust them?
King drops one further hint about the frustrations of being an insider with limited powers, two if you count the short-termism of politicians who need to get re-elected. In the US where Congress can block the green aspirations of a President McCain or Obama, King learned the trick of picking up the desk photo of the obstructive politician's grandchildren to observe " Well, I hope you're right about this." Politicians are like everyone else: they want their grandchildren to have a future.
As we left, the man in the next seat to me opined that King will be happier outside government because he can speak his mind. I'm not convinced. Nicholas Stern was appointed by chancellor Gordon Brown to do his climate change study precisely because he was an insider, former chief economist at the World Bank, a man who could not be dismissed as a lobbyist or crank - except by ex-chancellor Nigel Lawson in a cranky book of his own.
Stern now regrets that he understated his case for urgent action and the costs of delay. King reminded his audience in Hay today of the forces of conservatism. "Every research council has a chief executive at arm's length from government. Whenever in government I tried to interfere with their actions, I was fended off. We need people like you to write and say 'why aren't you spending more money?'"
The awkward fact is that climate change research still gets a fraction of the money going into particle physics research. Given the pressing nature of the problem, King admitted, it should be the other way around.
