No foreign leader can now speak freely with Donald Trump without expecting to read the contents of the conversation on the front page in the coming months.

Lamenting this in The Atlantic magazine, former George W. Bush adviser David Frum, a member of the so-called "never Trump" faction of the Republican Party, observed, "The temptation [to leak] is obvious: Senior national-security professionals regard Trump as something between (at best) a reckless incompetent doofus and (at worst) an outright Russian espionage asset. The fear that a Russian mole has burrowed into the Oval Office may justify, to some, the most extreme actions against that suspected mole.

"The nature of this particular leak suggests just such a national-security establishment origin. It is a very elegantly designed leak. The two transcripts belong to calls whose substance was already widely reported in the media; they give away nothing new."

The leak also brings to mind a telling observation by Anthony Scaramucci, the White House head of communications sacked last week after serving almost 11 full days. During one of his few public outings, he observed that some senior White House staff seemed determined to protect the American people from the President. (To be clear, he said this as though it was a bad thing.)

Frum is right. The new leak reveals little extra information, but it confirms a great deal.

It confirms that, despite Trump's faint grasp of international affairs, he blithely made calls to crucial allies without preparation and the support of the State Department, the world's largest diplomatic machine, now lying idle a few blocks from the Oval Office.

It reveals that Trump is as bombastic, narcissistic and argumentative on the phone to the leaders of friendly nations as he is on the campaign trail.

It suggests that, despite recent sackings and the installation of Marine general John Kelly as chief of staff, Trump has failed to bring basic order to his White House.

And it reminds us how much more comfortable Trump is speaking to Russian President Vladimir Putin than to American allies.

"Putin was a pleasant call," Trump told Australian Prime Minister Malcolm Turnbull. "This is ridiculous."

The last point is resonating today in the US with news that Robert Mueller, the special counsel prosecutor investigating allegations of Trump campaign collusion with Russia has empanelled a grand jury.

In the US system, a grand jury has powers similar to those of a royal commission. It can compel testimony and the production of documents. Worse, from Trump's point of view, Mueller has made it clear he has broadened his investigation to look into Trump's business dealings with Russian contacts.

The empanelling of the grand jury confirms that Mueller, who has recently hired new high-powered legal staff, expects this investigation to continue at length, and believes there is a good chance that it will recommend that charges be laid against members of Trump's campaign team.

As his investigation picks up steam, Congress has made it clear it is determined to protect him.

To date, Trump has fired three officials who were investigating him - FBI director James Comey, New York state US attorney Preet Bharara, and acting head of the Department of Justice Sally Yates.

Bills with bipartisan support designed to protect Mueller from the same fate are progressing through both houses of Congress.