Donald Trump did something he has never done before on Saturday - he tweeted Robert Mueller’s name.

“The Mueller probe should never have been started,” the US president wrote, addressing the man leading the Russian investigation.

A second tweet swiftly followed, asking “why does the Mueller team have 13 hardened Democrats, some big Crooked Hillary supporters, and Zero Republicans?”

On Wednesday, Mr Trump was at it again, quoting a Harvard lawyer who said Mr Mueller was "told to find crimes, whether a crime exists or not”.

For Trump watchers, these messages carry more significance than the average presidential tweetstorm - they indicate a step-change in approach to the special counsel.

The signs of a new stance are many; the potential impact on his presidency profound. Is Mr Trump now preparing for all-out war with Mr Mueller?

White House enters the loop

The investigation into Russian election meddling, handed to Mr Mueller when FBI director James Comey was fired, is the dark cloud that hangs over the Trump presidency.

Prospective end dates for the probe touted by Mr Trump’s lawyers - first Thanksgiving, then Christmas, then early in the New Year - have come and gone.

All the while, the full scale of the inquiries has begun to become clear, with obstruction of justice claims and Mr Trump’s business activities now facing scrutiny.