The story of a Russian spy, Kremlin cash and Reform

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

- Ben Quinn, Luke Harding, Artem Mazhulin and Peter Walker

At 6ft 4ins (1.93 metres), 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 Mormon 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 1960s.

Gill's humiliation is not just personal. His links to Russia raise awkward questions for Reform UK, and for its leader, Nigel Farage, for whom Gill was a key lieutenant when they were in Brussels. While Farage has been trying to distance himself from Gill, sources who worked with them in Brussels have told the Guardian the two men used to be close.

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

FBI agents stopped Oleg Voloshyn, a pro-Kremlin Ukrainian politician close to Viktor Medvedchuk, a Ukrainian oligarch sometimes known in his native country as the "dark prince" and a long-term ally and friend of Vladimir Putin.

It was less than a year before Russia's full-scale invasion of Ukraine, but Medvedchuk had already been charged with treason while his TV channels, conduits for Russian propaganda, had been taken off the air.

Voloshyn, his envoy to the west, was in the crosshairs of US authorities.