During his time in the UK, Yang Tengbo created and operated a range of entities, interests and trade associations. The most intriguing is a company with a direct connection with one of Prince Andrew’s closest advisers.

In 2005, three years after he moved to the UK, Yang set up his principal company, Hampton Group International. Originally called Newland UK, its earliest accounts describe it as a tour operator rather than any form of consultancy. It appears to have been a quiet success, with an annual turnover of £1m just five years into its operations.

Newland changed its name to Hampton in 2020. Although by this time it had stopped reporting its turnover, its balance sheet suggests it remained financially very comfortable, with £7m in assets, almost half of which was cash.

It was two years later that Yang went into business with an associate of Prince Andrew.

Dominic Hampshire is described in the immigration tribunal judgment against Yang as a “senior adviser” to the Duke of York. He was previously a director of a company called Lincelles, reportedly intended to act as a trust fund for Andrew’s daughters. Lincelles was closed down in 2022, supposedly after never having conducted any business.

Later the same year, Hampshire became a director of a management consultancy firm called Eurasia Global Partners. Little is known about the company, and there are almost no filings relating to its activities on Companies House.

What little is revealed about Eurasia mostly emerges from its incorporation papers, which show 30% of its share capital was owned by Yang, and a further 10% owned by Hampshire’s consultancy firm. The remaining 60% of the shares were owned by a firm called Albe Global Partners, owned by a former commodities trader and the former boss of the oil firm Tullow.

It is unclear whether Eurasia Global Partners is linked to an entity called the Eurasia Fund that is mentioned in the immigration tribunal’s judgment. The judgment refers to “another letter from Mr Hampshire to [Yang] dated 22 October 2020, confirming that [Yang] was authorised to act on behalf of the duke on an international financial initiative known as the Eurasia Fund in engagements with potential partners and investors in China”.

A source familiar with Eurasia Global Partners said it had been intended to facilitate Chinese investment in renewables projects in Africa, but that the company failed to get off the ground and never traded.

Nonetheless what is striking from the timeline is that Hampshire went into business with Yang a year after the alleged spy was first stopped by the British security services.

According to the special immigration appeals commission (Siac) judgment, Yang had been stopped and searched at the border in November 2021. There is no suggestion that Hampshire or the other investors were aware of Yang being stopped.

Copies of his electronic devices were obtained and examined. It was these searches that resulted in the discovery of Hampshire’s unctuous correspondence with Yang, in which he assured him of the Duke of York’s favour.

“I also hope that it is clear to you where you sit with my principal and indeed his family,” Hampshire wrote. “You should never underestimate the strength of that relationship … outside of his closest internal confidants, you sit at the very top of a tree that many, many people would like to be on.”

It was in February 2023 – three months after his company invested in Eurasia Global Partners – that Yang was informed that the home secretary had directed that he should be effectively banned from entering the UK.

In a statement issued after a ruling on Monday allowing him to be named, Yang said he had “done nothing wrong or unlawful”. His statement described the “widespread description of me as a ‘spy’ [as] entirely untrue”.