In Seattle there is little clean-tech buzz beyond a massive biodiesel company, Imperium Renewables, founded in 2004.

ECONOMIST: America's clean-tech clusters

All of the historians involved in the debate over decline agree that the age of American Imperium cannot go on forever.

BBC: Is the United States an empire in decline?

It had not willed an Islamic imperium, but it had gotten one.

CENTERFORSECURITYPOLICY: Obama��s Afghan struggle

He expanded the Democratic imperium to include Colorado, New Mexico and Nevada.

ECONOMIST: The presidency

The bureaucratic screw-ups of the late Blair imperium, mostly in the Home Office, had threatened to revive an old caricature of Labour incompetence.

ECONOMIST: It might win Gordon Brown an election. But then what?

Alarmed by the prospect of a new American imperium, European leaders will once again try to use the United Nations to rein in America.

ECONOMIST: Charlemagne

Thank you for the opportunity to be here at Imperium Renewables.

NPR: Does Backing Biofuels with Public Money Work?

But the role Mr Johnson would have to fill would be shaped by the peculiar circumstances that elevated him, and by the ebbing dynamics of the last months of Labour's long imperium.

ECONOMIST: Bagehot