The US has determined that Saudi Arabia’s de facto leader – Crown Prince Mohammed bin Salman – has immunity from a lawsuit filed by murdered journalist Jamal Khashoggi’s fiancé.

Mr Khashoggi, a prominent Saudi critic, was murdered at the Saudi consulate in Istanbul in October 2018.

US intelligence has said it believes Prince Mohammed ordered the killing.

But in court filings, the US State department said he has immunity due to his new role as Saudi prime minister.

Mr Khashoggi’s ex-fiancé, Hatice Cengiz, wrote on Twitter that “Jamal died again today” with the ruling.

She – along with the human rights group Democracy for the Arab World Now (Dawn), founded by Mr Khashoggi – had been seeking unspecified damages in the US from the crown prince for her fiancé’s murder.

The complaint accused the Saudi leader and his officials of having “kidnapped, bound, drugged and tortured, and assassinated US-resident journalist and democracy advocate Jamal Khashoggi”.

The secretary general of Amnesty International, Agnes Callamard, said: “Today it is immunity. It all adds up to impunity.”

The official explanation for this granting of immunity to a man the CIA suspects was complicit in Mr Khashoggi’s murder is that the Saudi crown prince’s status formally changed in September when he was named prime minister. But this change is largely academic.

In Saudi Arabia power rests with the King, the crown prince and the immediate, blood-related royals. MBS, as the crown prince is known, has been all-powerful since soon after he became crown prince in 2017.

It was always highly unlikely that the US, as Saudi Arabia’s strategic partner and arms supplier, was ever going to facilitate the arrest of MBS. But granting him immunity in this way will cause some relief in the Saudi royal court and has provoked a storm of protest from human rights groups as well as Mr Khashoggi’s fiancée.

Underlying all this is Washington’s desire to improve its poor relations with the Saudi leadership. It