How green is the Queen? Her Majesty is, of course, scrupulous in avoiding making public pronouncements on political issues, as environmental ones – and especially climate change – have become. But every so often indications emerge that she is privately very environmentally conscious, and is especially concerned about global warming.

One such surfaced recently when it was reported that – at a private lunch at Buckingham Palace attended by Dame Julia Slingo, the Met Office's Chief Scientist, last week – she had talked about unprecedented flooding at Balmoral this summer and “wondered if it was caused by climate change”. The report echoes an eyewitness account by Sir Richard Branson in his recent book, Screw Business as Usual, of the Queen and Barack Obama “animatedly” discussing global warming over dinner.

Indeed, her concern goes back a long way, at least until the Nineties. In October 1997 she seriously contemplated including a passage on global warming in her speech to a Commonwealth Prime Ministers' conference. Experts on the issue were discreetly sounded out on what it might be “helpful” for her to say, and ministerial aides told to “expect something green from the Queen.”

In the event the intervention was toned down to an oblique reference to “environmental challenges, which especially affect the smaller states”. Even this was interpreted as a coded rebuke to the then Australian premier, John Howard, who had attacked a scientific prediction that several low-lying Pacific states would eventually sink beneath rising seas as “an extremely exaggerated statement, and not one that impresses me.”

But it was seven years later that the Queen gave her clearest ever indication of her sympathies. In November 2004 – on the very day that George W Bush was elected to his second presidential term, as it happens – she diverted from a state visit to Germany to open a high-level Anglo-German meeting in Berlin on combating climate change. I was there, and senior Buckingham Palace sources assured me that they could not remember a similar occasion when she had similarly chosen to open a conference on such a sensitive international issue.

And she practices what she takes care not publicly to preach. Famous for going round the Palace, switching off the lights, she was quick to move over to the often unpopular energy-saving light bulbs. She was similarly early in adopting recycling, adapted her “most-used” Bentley to run on LPG, and double-glazed skylights.

She installed two combined heat and power plants – greatly increasing energy efficiency by producing both electricity and hot water for heating – more than a decade before Owen Paterson discovered them this autumn as a key way to combat climate change, and had water-saving “hippos” inserted in the tanks of the royal lavatories.

Prince Philip – who started the family's concern about the environment in the Fifties, and was a long-serving international president of the World Wildlife Fund – recently signalled less enthusiasm about combating climate change, hosting an event last year to mark climate sceptic David Bellamy's 80th birthday. But his concern is less outright scepticism, I am told, but over how concentrating attention on the issue may have made environmental concern more anthropocentric at the expense of emphasising the need to conserve nature for its own sake.

Prince Charles, of course, is one of the world's most prominent and long-standing campaigners for the environment and against global warming. It seems that his mother stands quietly behind him.

Telegraph.co.uk