Chris Huhne's departure from the Department of Energy and Climate Change (Decc) sees the exit of a minister who is generally regarded as having fought tenaciously for "green" policies within the Cabinet.
And it raises the question of what hue the self-proclaimed "greenest ever government" is likely to be in future.
It is a barely-guarded secret that other departments, notably the Treasury, are markedly less keen on policies such as increasing renewable electricity than Mr Huhne's team.
He has been a feisty negotiator, unafraid to take on the Treasury and other opponents in public and in private.
"He's proved a determined and efficient climate change secretary," said Tony Juniper, former head of Friends of the Earth UK and now a consultant on environment and sustainability issues.
"Given that the broader Cabinet has not demonstrated any deep green commitment, his departure does raise concerns about the government's overall direction on this issue," he told BBC News.
Similar plaudits have come in from other environment groups and from the renewable energy industry, the only exception being from solar power companies angered by the recent fiasco over feed-in tariffs.
That issue, damaging as it was, has in reality been a sideshow.
The big picture is that the government's "greenest ever" pledge has been undermined by the row over selling off public forests, badger culling, and above all by changes to planning regulations that appeared, as one critic said, "to blame the recession on too much protection for dormice".
Another long-time observer, speaking anonymously, said that climate change was now the only area in which the government could be said to be "green" at all - though others would point to developments such as Defra's Payment for Ecosystem Services (PES) work as proof that a green heart still beats somewhere in Whitehall.
On the international side, Chris Huhne played significant roles in the last two UN climate meetings in Cancun, Mexico and Durban, South Africa.
Despite having had only seven months in the job, he was one of 10 ministers chosen by the Mexican host government to pull the Cancun talks around when they appeared to be heading for the rocks.
And in Durban, he was in the vanguard of EU moves to build a novel and powerful coalition between Europe and scores of the world's poorest and most climate-vulnerable countries, which ultimately secured agreement to negotiate a new global agreement with legal force by 2015.
His replacement, Ed Davey, therefore steps into a role that is more significant than it might first appear and he makes the short walk from the Department for Business, Innovation and Skills (Bis).
Whether he can fill the relatively large and rumbustious shoes of Chris Huhne is a subject of speculation and some anguish among the environmentally concerned.
But Matt Spencer, director of Green Alliance, suggests there may be a different but equally effective way for Mr Davey to do business.
"It's useful that he's coming from Bis, because Decc and Bis really need to work together to ensure policies that deliver, and are more joined up across the two departments," he said.
"Chris Huhne excelled at tough negotiation, but Ed Davey has the opportunity to build a broader alliance across government.
"Chris's departure also offers an opportunity for the PM and Deputy PM to re-assert their support for a low-carbon agenda."
Mr Davey's voting record in Parliament suggests he is fully signed-up to a clean energy agenda - though that is hardly surprising as it has long been a Lib Dem priority.
In the last few years, he has also signed Early-Day Motions endorsing the reality of man-made global warming, opposing mega-dairies and calling for more protection for UK nature.
Ones he has signed that might come back to haunt him are those opposing hidden subsidies for nuclear power and requesting more financial support for the solar energy industry.
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