Ties have been tested more recently, however, by the impetuous and ruthlessly ambitious young Crown Prince Mohammed bin Salman, who effectively took over the business of running the country from his aging father King Salman in 2015. It’s no secret Washington would have much preferred the king’s more cool-headed nephew, Prince Mohammed bin Nayef.

The Crown Prince, or MBS, as he is known, had pitched himself as a reformer, who was going to drag Saudi into the modern age. But the 35-year-old prince has launched a crackdown of opponents, arrested female activists demanding the right to drive and even members of his own family, as well as waged a devastating war in neighbouring Yemen.

The gruesome killing of Khashoggi, a US resident and prominent Washington Post columnist, however, crossed the line.

Since taking office in January, Mr Biden has ordered a review of the US’s arm sales to Saudi and cut off military support for the conflict in Yemen. But Friday’s limited sanctions against members of the Saudi hit squad who killed Khashoggi, while sparing MBS himself, show that the new administration is as toothless as the previous one when it comes to the Saudi royal family.

It let the prince - quite literally - get away with murder.

While the newly declassified US intelligence report leaves officials in no doubt that Prince Mohammed ordered the 2018 killing, they know a move to target him directly would make it impossible to deal with the Saudis in the future.

“Joe Biden has decided the cost of penalising Saudi Arabia’s crown prince, Mohammed bin Salman, is too high,“ wrote Laurence Tribe, co-founder of the American Constitution Society. “It’s deeply disappointing.”

He seemed to sum up the feelings of critics and exiled Saudi activists across the world who have been calling for international powers to take decisive action.

It was notable that Khashoggi was not even mentioned in the readout of the call between Mr Biden and King Salman on Thursday. It could be interpreted as a deliberate and mutually-agreed omission, designed to give the message: This is not down to Saudi Arabia; this is just down to MBS.

Mr Biden has made it clear that he will not be dealing directly with MBS from here on in, only communicating with his “counterpart”, which as head of state would be the king himself.

But what will that mean for MBS? Will he continue to operate as the kingdom’s de facto ruler, or will his father look to rein him in and replace him with a more controllable alternative?

It remains to be seen.

King Salman, who is 85 and in poor health, will loathe to appear to capitulate to US will, but will need to choose a successor soon. Prince Nayef was arrested in 2017 and is now under arrest, accused of corruption and plotting against the crown prince.

Mr Biden’s aides say that as a practical matter, MBS would not be invited to the US anytime soon, nor will they conduct official business with him in future.

For now, MBS has escaped with a mere tap on the wrist, and the US-Saudi relationship emerges battered, but still very much alive.