The 28-year-old admits he had other options, but was quickly sold on the new enterprise when he spoke to team principle Tony Fernandes and technical director Mike Gascoyne.
Robert Gascoyne-Cecil, the 7th Marquess of Salisbury, said it hoped to capitalise on the "great success" of the Henry Moore exhibition, which celebrated the house's 400th anniversary in 2011.
Virgin had their car out on the Silverstone track at the end of last week, but Gascoyne says Lotus are following hot on their heels ahead of Friday's official launch.
Gascoyne shrugged off those observers who had said Renault had only achieved qualifying positions of third and fourth, with Alonso ahead of Jarno Trulli, by running the cars light on fuel.