'IN THE Walker Art Gallery there's a painting that inspired the world's most powerful man when he was still just an ordinary dreamer.

Created in the late-1800s, George Frederic Watts' allegory of hope shows the concept as a hunched, blindfolded figure in a blue dress, clutching a battered lyre with only one string.

It was upon a version of this work that Barack Obama's former pastor Jeremiah Wright based a sermon about the audacity of hope - a phrase the future US president would later borrow for his tidechanging 2004 Democratic National Convention keynote address and the title of his second book.

The fact that one of Watt's Hope paintings hangs in The Walker is one reason artist Nicola Green chose the gallery to host the UK premiere of her series of silkscreen prints, which document Obama's 2008 presidential campaign.

Her exhibition, In Seven Days, based on her experiences of the campaign trail across the US, opens on January 18 - three days before his second inauguration.

London-based Green (whose grandfather was from Liverpool) gained unprecedented access for a British artist, making six trips to the US, beginning with Obama's nomination acceptance in Denver in August 2008 and ending with his inauguration in Washington in January 2009.

In that time, she took around 2,500 photographs and filled sketchbook after sketchbook, some of which fill the seven glass display cabinets that will accompany her seven silkscreen prints based on themes inspired by what she witnessed.

Her first meeting with Obama was during a rally in New Hampshire.

"He asked me after his speech if he could see my drawings and I said 'no'," she admits.

"He really laughed. I said, 'You wouldn't show me a half written speech'.

"He's very warm and very much like you would expect him to be. He's astoundingly inspiring as a speaker and it was incredible to have had the opportunity to listen to him speaking to all different kind of communities and different sizes of audiences across America."

Green was drawn to Obama's story when her husband, Tottenham MP David Lammy and a fellow Harvard Law graduate, met him and a third prominent black politician at an event held at the Massachusetts university in 2005. At the time she was pregnant with her first son and had started to think about what it would be like for him to be a mixed race boy growing up in the 21st century.

Obama had not yet publicly stated that he would like to run for president but had mentioned it during the Harvard event.

"I had never heard of him," says Green.

"But as a white mother about to have a mixed race boy I really started thinking about issues of identity and role models for him.

"The idea of this guy running for president, which was a pretty radical idea at the time that actually nobody took seriously to begin with, really encapsulated a lot of those themes."

Several years later, this time pregnant with her second son, she heard Michelle Obama speaking in London. It compelled her to contact the Illinois senator and request permission to create his portrait.

It was while watching him accept the nomination for candidacy that she realised her single piece of work should instead be an entire series.

"I was sitting in the crowd with 70,000 people in that massive stadium, which is open air and it was night time, and it was coincidentally the 40th anniversary of the Martin Luther King I Have a Dream speech so it was an extraordinary moment.

"It seemed to me the energy of the 70,000 people in that stadium reflected the energy and interest of people all around the world. I realised the portrait was bigger than a picture of just that one man. It was the story of all of us around the world and what his candidacy might mean for us."

Her first piece of work, Light, which represents day one in her seven day series, is a circle of gesticulating hands. It symbolises the Mexican wave carried out in the stadium that night but also the hand of a clock and suggests the shape of a clock and the idea that at that very moment the whole world was concentrated on a single event.

Day four of the series, entitled Change, is a black and white portrait of Obama standing in a relaxed yet determined pose. This is based on Green's attendance at a rally in Philadelphia in October 2008, which a campaigner later told her was the turning point in Obama's victory.

"The work can be understood on a number of different levels but what I really wanted to capture was this sense of what it really means to achieve something that is seemingly impossible," she says.

Had Obama not won the election, In Seven Days would have been about dashed hopes rather than a dream realised. Since he did however, and has gone on to win a second term, perceptions of race have shifted.

Green relates the experience of Kirk Hanlin, a senior member of the campaign team, who was approached by a little boy as he stood at the front of a podium before the president arrived to give a speech during the 2012 campaign.

"Are you the president?" asked the boy and, when Hanlin replied 'no', tried again: "Are you the mayor?"

So Hanlin, who is white, knelt down and said: "Here's how you can tell I'm not either, because your mayor and your president are black just like you."

"Kirk told me he worked for Clinton and he's worked in the White House for years but that was the moment that he really understood what this story might mean for our children," says Green, whose elder son learned the name "Obama" from TV news reports and conversations around him when he was still a toddler.

"Before, even for us watching that story unfold, it seemed like it was going to be impossible for a black man to become president. For them it's possible because it happened."

IN SEVEN Days is at The Walker from January 18 to April 14.'