On a miserable, rainy day in Concord, New Hampshire, he asked to look at her sketches. But British artist Nicola Green was adamant: "I said, 'No! You wouldn't show me your half-finished speech.'"

Barack Obama laughed and agreed – although if he visited the Walker art gallery in Liverpool now he could actually see the drawings in a vitrine along with the seven silkscreen prints that Green made to tell the story of the 2008 presidential campaign.

The artist was given remarkable access to the campaign, making six trips beginning with Obama's nomination acceptance speech in Denver and ending with his inauguration in Washington DC. The results, based on a huge number of drawings, photographs and conversations, are works collectively called In Seven Days … and this is their first appearance in the UK after first going on display at Harvard Law School two years ago.

The US Library of Congress and the Met in New York have acquired sets of the works , which Green described as a deconstruction of what hope really is, a reflection on what future generations can take from the events.

The project came about because Green's husband, the black Labour MP David Lammy, knew Obama and returned from a trip saying he was thinking of running for president.

Green was pregnant with the couple's first son. "I started thinking, as a white mother, about my children and what the world would look like for them and how their experience of the world would be different from mine. I was thinking of who the role models for them would be outside of popular culture and started thinking of what this man, who looks like my boys, would mean for them."

By 2008, when their second son was born, she'd asked Obama if she could visit and produce a portrait. After experiencing the electrifying atmosphere of the Mile High stadium in Denver where he accepted the nomination, she realised it was a much bigger story than just one man; that she had to do more than a portrait.

Green sketched, took photos, talked to people – but deliberately did not tell anyone other than family what she was doing or where she was going. "I was thinking about history, backwards, now and in the future, I wasn't wrapped up in the news media cycle.

"It was a process of distilling and reflecting on all the symbolism and imagery and experiences and making a set of work that would be relevant for our children – I felt I had to have a kind of monastic, studio life."

It took Green two years. The Liverpool show opens on Friday – ahead of Obama's second inauguration on 21 January – and runs until 14 April.