The fragile trade truce between Washington and Beijing is fracturing. I am told that British intelligence assets have been shuttling between the White House and Zhongnanhai for the past 72 hours. The goal: keep the peace deal from collapsing entirely.

Sources in the Foreign Office confirm that MI6 officers have been holding secret meetings with Chinese trade officials in a neutral European capital. The Americans are aware, but only just. There is a growing sense in the West Wing that President Xi is stalling. The trade war ceasefire agreed at the G20 is unravelling faster than anyone expected.

A senior UK government source told me: "The Chinese are pushing for more concessions on tech transfers. The Americans are demanding immediate action on intellectual property. Both sides are entrenched. We are trying to find a middle ground."

The timing is awkward for Downing Street. The PM is already fighting her own battles. The Brexit vote is looming. A full-blown US-China trade war would send shockwaves through the global economy. The Treasury is watching closely.

One backbench Conservative MP, a former minister, described the UK's role as "necessary but risky". He added: "We risk getting caught between two elephants. But if we can pull this off, it secures our position as a key global broker."

But not everyone is convinced. Labour's shadow foreign secretary accused the government of "meddling without a mandate". She said: "The UK should not be acting as a secret go-between for two superpowers. Where is the parliamentary scrutiny?"

Privately, Whitehall insiders admit the talks are a delicate balancing act. Leaks could derail everything. The British diplomat leading the effort is described as a China hand with decades of experience. He is known for his discretion. But in a city where everyone talks, secrets have a short shelf life.

The Chinese embassy in London declined to comment. The US ambassador's office did not respond to requests.

What happens next? If the back-channel talks fail, expect a ratcheting up of tariffs within weeks. That would hit British exports too. No wonder the PM is letting her intelligence chiefs run this one.

I will keep you posted as this develops. For now, the truce is holding by a thread. And UK is holding the needle.