When US President George HW Bush craved "a smoking gun" in 1992 to politically kneecap his White House challenger Bill Clinton, the British government delved into its files for damaging information. So, did the Bush camp solicit foreign interference to help him win an election - the allegation that has seen President Trump impeached?

"A guy like that doesn't deserve to be president," President Bush told his sister about Clinton.

He viewed the young Arkansas governor, who was the same age as Bush's eldest son, as a scoundrel and felt confident he could roll over him.

But the president sorely underestimated Clinton, an adversary so politically gifted that his ascent to the White House had been foreseen when he was aged just seven by his school teacher.

To Bush's mystification, his saxophone-tootling challenger's popularity in opinion polls was even defying the gravity of revelations about his draft-dodging past.

The Republican, a decorated World War 2 fighter pilot, dictated to his diary: "I'm tired of this guy lying and ducking on the draft and not coming clean."

Bush had another problem - his campaign was as stale as the recession-sapped US economy.

So he turned for inspiration across the Atlantic to his friend, UK Prime Minister John Major.