The first thing most people recall about Nathan Gill is his imposing height.

At 193cm (6ft 4in), the one-time Reform UK leader in Wales towered over colleagues and opponents – and he was taller still in his favourite cowboy boots.

Other than that, the softly-spoken 52-year-old was a largely unremarkable presence among the more colourful characters in Nigel Farage’s parties.

Until recently, political profiles have dwelt on Gill’s politically quirky status: the teetotal member of the Church of Jesus Christ of Latter-day Saints who bore Ukip’s flag in the Senedd, even if opponents charged that he was often absent.

Yet his legacy is now a very different and disturbing one. This month he will be sentenced at the Old Bailey after pleading guilty to taking bribes to make statements in favour of Russia during his tenure as a member of the European parliament.

In modern British politics, it is an almost unique fall from grace – perhaps with parallels to the story of John Stonehouse, the high-flying Labour MP recruited as a spy for Czech intelligence in the early 60s.

But Gill’s humiliation isn’t just personal. His links to Russia raise awkward questions for Reform UK, and for its leader, Nigel Farage – Gill was a key lieutenant of his when they were both in Brussels. While Farage has been trying to distance himself from Gill, multiple sources who worked with them in Brussels have told the Guardian that the two men used to be close.

View image in fullscreen Farage (left), then Ukip leader, and Gill before a plenary session at the EU headquarters in Brussels in June 2016, just after the Brexit vote. Photograph: John Thys/AFP/Getty Images

The moment of Gill’s downfall dates back to July 2021 and the arrivals queue at Washington DC’s Dulles international airport.

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