Why did Trump just gift Saudi Arabia a nuclear win?

Donald Trump has announced a landmark nuclear deal with Saudi Arabia while pressing ahead with efforts to stop Tehran from developing a nuclear weapon. What’s driving Trump’s new agreement with Riyadh? And how is it likely to be received at home and across the Gulf? Jonathan Freedland speaks to Robert Jimison, who covers Congress for the New York Times with a focus on defence and foreign policy, about what the agreement contains, why it matters and the political challenges it could face.