“It’s hard not to think about it,” Andy Robertson says as he looks forward to the Champions League final after the Liverpool left-back has reflected for 45 minutes on his uplifting story from being a Celtic reject and relegated with Hull City a year ago to facing Cristiano Ronaldo and Real Madrid in Kiev this Saturday. “When you’re lying in bed you just think: ‘What if?’”

Robertson’s freckly face breaks into a helpless smile. He has fought hard to reach this point but the 24-year-old Scot allows himself to enjoy the fleeting anticipation of Liverpool possibly becoming European champions for a sixth time with Robertson as one of their new cult heroes. “That’s natural,” he says during a break at Liverpool’s training camp in Marbella. “Real Madrid have been to three finals in the last four years so they’ll do the same.”

Milan’s Suso: ‘I feel like I am only at 70% of what I can achieve’ Read more

He taps his temple thoughtfully. “But the head is the worst part of the body because it can let you wonder. It’s about making those happy thoughts a reality. Of course we believe we can win it – but we know how hard a task we face.”

Robertson’s emergence as one of the stories of the season was sealed against a previously rampant Manchester City in the quarter-finals. Liverpool tore City to shreds in the first leg, with Robertson full of high-energy commitment throughout both games, and secured a 5-1 aggregate win. He was then outstanding, home and away, in the semi-final against Roma.

“Everyone is nervous in these games but it’s about using your nerves in the right way. Some people shy away from it but others use the nerves in a very positive way. Against City at Anfield, all 11 of us stood up to the pressure. And in the second game we showed a side we’ve not always shown. After the worst-possible start [conceding an early goal] we defended really well and gave them no chances.”

Robertson is an enjoyable interviewee because, amid Champions League fervour, he remains grounded and chockful of amusing anecdotes about how different his life was a few years ago. In 2013, while playing as an amateur for Queen’s Park and working part-time for the Scottish FA at Hampden Park, he would take telephone bookings on the phone for games and concerts. He also worked on match days.

Facebook Twitter Pinterest Andy Robertson, second from left, celebrates Liverpool’s equaliser during the second leg of the Champions League quarter-final against Manchester City at the Etihad. Photograph: Laurence Griffiths/Getty Images,

“I once showed Vincent Kompany to his seat,” he says, imagining how bemused he would have been then had he known that four-and-a-half-years later he, rather than the Belgium international and Manchester City captain, would appear in a Champions League final. “Scotland played Belgium and I was told to show [the injured] Kompany to his seat and give him a programme. He won’t remember it.”

Emre Can to move from Liverpool to Juventus on five-year contract Read more

Mo Salah is the player of the season but Robertson represents another incredible bargain. Having been part of two relegated Hull teams, while winning promotion from the Championship in his middle season, Robertson was signed last summer for an initial fee of £8m. The response from Liverpool’s supporters was underwhelming. Eleven months later Robertson is an Anfield favourite, alongside Salah, and they share a hospitality box.

“Mo’s family and friends have been lovely to my family. We come from completely different backgrounds but they get on so well. My family got a picture with him when Mo walked in last Sunday [after Salah had been awarded the Golden Boot].”

Robertson and his girlfriend Rachel are parents to Rocco, who “will be nine months on the day of the final. Rachel was the year below me in school [near Glasgow], but we hung about with the same friends. We got together when I was 19. She always winds me up. There was a memory on Facebook from eight years ago and I wished her happy birthday just after midnight. She says now: ‘Yeah, that was you trying to get in early doors.’ Obviously, being a proud man, I denied it. But she might have a point.”

Beneath the chuckling self-deprecation there are serious points to make about Robertson’s conviction. “I always believed in my ability,” he says intently. “I just had to work hard and be patient and, yeah, at times it didn’t look likely. You need a wee stroke of luck but every chance I’ve been given, I’ve taken.”

Sign up to The Recap, our weekly email of editors’ picks.

Robertson was cut from the Celtic academy for being too small at 15. “If you’re let go from Celtic, the club you support, and go to Queen’s Park, people think it’s a disaster. I don’t think I cried but I was very upset. As a young boy your dream has been taken away. But I had good people around me and it was probably the best thing that happened.”

Three years later, Robertson was playing for Queen’s Park in the lowest tier of Scottish professional football. “At Queen’s Park you just got your travel expenses so I found a job on the tills at M&S on Sauchiehall Street in Glasgow.”

A newspaper recently dug out a Robertson tweet from just before then in August 2012: “Life at this age is rubbish with no money. #needajob.” Robertson looks embarrassed but points out: “Life is like that for many young people.”

He had made his Queen’s Park debut against Berwick in the Irn-Bru Cup in July 2012, in front of a crowd of 372. “Rangers were in our division then and so we also played at a full Ibrox – 50,000 – and it was a great experience. We got beaten 2-0 but it was tight until the 87th minute. I missed a glorious chance which I’m always reminded of by old team-mates. I then got offered my first professional contract at Dundee United [in 2013]. The manager Jackie McNamara had been a great full-back [at Celtic] and he helped me.”

In July 2014, Robertson moved to Hull for £2.85m. “I got off to a flyer but then I injured my ankle. I couldn’t get back in the team and we got relegated. But the Championship season was massive. Steve Bruce really put his trust in me and I learnt so much. But the gaffer fell out with the club and we went into the Premier League with 12 players. Then in January we had a wee turnaround when Marco Silva came in. He was brilliant but couldn’t keep us up.”

Facebook Twitter Pinterest Andrew Robertson in action for Queen’s Park against Rangers at Ibrox in 2012. Photograph: Kirk O'Rourke/Rangers FC/Press Association Images

Robertson joined Liverpool last July and recalls the impact Jürgen Klopp had on him. “When you meet a new manager you’re nervous and this was even more so because our gaffer is world famous. But he gave me one of his hugs and relaxed me from day one. The gaffer really wants to know you. I sat down with him and he told me about his past and I told him about mine. We both had to battle for everything. He liked my story and that helped.”

His man-of-the-match debut against Crystal Palace won approval from the Kop. “People were doubting me but I played quite well and I think the fans took to me. But my problem was Alberto [Moreno] was playing very well. It was frustrating but I had to watch and wait.”

Robertson only played three of the first 12 Premier League games and he was often not even in the squad. “The manager said: ‘We’ve got James Milner on the bench and he is so versatile. You need to learn how we play and improve defensively’. Such good communication really helped. It was unfortunate for Alberto he got injured and over the Christmas period I was the only left-back. Bournemouth away [a 4-0 win in mid-December] was a big performance. The gaffer was really happy with me.”

Liverpool then went to Arsenal and a madcap game ended 3-3 after the visitors shipped three goals in five minutes. Gary Neville expressed reservations about Robertson but six months later the Sky pundit picked the Liverpool left-back in his team of the season. “He’s a great pundit,” Robertson says, “and to make his team of the season means I changed his mind.” Robertson shares Klopp’s social conscience – even if he is uncomfortable that a personal gesture to a young supporter became public knowledge. When he heard that a seven-year-old Liverpool fan had donated his pocket money to a food bank, Robertson wrote to the little boy and sent him a shirt signed by Roberto Firmino because “nobody wants the left-back’s shirt.”

‘I don’t feel like an underdog’: Jürgen Klopp eager for Real redemption Read more

“It gathered pace [when his letter turned up on Twitter] which I didn’t want. The food bank is something I’ve always supported because there’s no excuse for anyone to go without food.”

For his 21st birthday, Robertson asked his family and friends to donate to their local food bank rather than buy him anything. “A normal 21st birthday present is a bottle of vodka or champagne and during the season I don’t drink. At the end of the season I have a few beers with my old man. So if someone wants to buy me a bottle of vodka I’d rather they donate the £20.”

It’s striking that Robertson asks me to downplay the food bank story – and a compassion that feels natural and low key to him.

There will be nothing low key about Kiev. How does he feel about facing Ronaldo in the final? “It’s a great challenge but the problem with Real Madrid is that they’re all fantastic players. If you focus on Ronaldo then somebody else will pop up. But we’ll have a game plan and look at all of their strengths and weaknesses.”

A year ago Robertson was facing another season in the Championship but, on Saturday night, an incredible turnaround will be complete. “Football is full of highs and lows but when people retire they often say: ‘I wish I’d enjoyed it more.’ I’m now playing at one of the biggest clubs in the world in a Champions League final. Of course there’s still that pressure but you need to enjoy it. I will.”