Donald Trump’s unpredictability makes him more dangerous than Richard Nixon, according to the former White House attorney who helped in the Watergate cover-up before co-operating with investigators against the only president to resign from office.

John Dean said the probe by special counsel Robert Mueller into the current administration could end up being more damaging to the US than the scandal that brought down Nixon in 1974.

Mr Dean’s central role in the cover-up that brought down a president gives him a unique insight into the pressure mounting on the White House and parallels that span the decades.

He told The Telegraph that the Nixon he knew was "an authoritarian personality" just like Mr Trump appeared to be. But there were important differences, mainly that Mr Nixon understood the presidency better.

“They're very different in their perception of the president's authority,” he said. “Trump is more dangerous because he doesn't know what he's doing. The danger is he could do anything.