During the meeting with President Xi, he offered a full UK-China meeting either in London or Beijing. The Chancellor Rachel Reeves will travel to China in the spring.
For his part, Mr Xi said there was “broad space” for both countries to co-operate on trade and investment, clean energy and health care.
The problem is all this could become otiose if Donald Trump imposes huge tariffs on Chinese imports and triggers a global trade war.
In wars, countries often have to take sides.
The President-elect has – through his government appointments – made clear that his priority is facing down what he sees as the challenge from China.
That is why he wants Europe to spend more on its defence – so he can deploy US forces to the Pacific.
And that is why Europeans are braced for fresh pressure from the US to adopt a tougher approach to China.
Many in the US think the UK and the EU are trying to curry favour in Beijing by being less hostile than Washington.
So the prime minister is trying to engage more closely with China, and at the very least be more consistent than his predecessors.
Whether that policy survives contact with the second Trump presidency remains to be seen.