“I wanted to do it and they wanted to come,” Kenny Dalglish says simply on a quiet morning in Liverpool as he remembers how, in April 1989, he led his daughter Kelly and son, Paul, past a vast sea of flowers covering the ground at Anfield and headed up onto the Kop to honour the 96 people who had died that month at Hillsborough. “The kids had been at the game and so it was traumatic for them but it was also an unforgettable experience on the Kop.”

Dalglish was then the 38-year-old manager of Liverpool. Kelly was 13 and Paul was 12. Liverpool had asked him to become their player-manager almost four years earlier, on 30 May 1985, the day after the Heysel Stadium disaster when 39 people lost their lives at the club’s European Cup final against Juventus.

Heysel and Hillsborough opened up a compassion and desire in Dalglish to help others that explains why, beyond his sumptuous brilliance as a footballer and the 20 major trophies he inspired Liverpool to win as a player and a manager, he remains so revered on Merseyside. But in his company it is easy to forget the King Kenny mythology and to warm to him as the most human, if complicated, of men.

A moving and powerful new film, Kenny, captures all that Dalglish achieved and endured during his playing career and first managerial stint at Liverpool. It is made even more resonant by the usually reticent Dalglish’s willingness to talk relatively openly. The participation of his four children and wife, Marina, alongside old family film of them at home, adds to the poignancy.

Dalglish admits he never spoke about Hillsborough. So was his decision to take Kelly and Paul on to the Kop a way of sharing some of his turbulent emotions without discussing them? “I’m sure the deed was greater than a million words about it would have been. The two kids had gone straight back to school after Hillsborough and it felt important to show them how simplistic but beautiful it was on the Kop. It was better than me trying to explain things.”

He smiles wryly. “We took them out of school – and we’d be fined if we did that today. But how great was the education for them that day? Paul said he wanted to put his teddies up. So I took them in on the Friday morning and tied them up before anyone was in.”

There is a pause as the 66-year-old Dalglish remembers tying the teddy bears, one in Celtic hoops and the other in Liverpool red, to the terraces at an empty Anfield all those years ago.

In the film, Paul describes how, on the Kop, he finally broke down and cried in his father’s arms. But as Kelly Cates, Dalglish’s eldest daughter and an accomplished football broadcaster, suggests, her dad never addressed his own grief. “My only thought was to help somebody else,” he says. “If it means you cut yourself out of the deal that was no problem for me. If somebody else needed you, you helped them. Marina and I were brought up that way. Her mum and dad came down from Glasgow to look after the kids while we were at the funerals. I wouldn’t change what I did. Whether or not I’ve missed out looking after myself doesn’t matter. You can handle that.”

Dalglish is a product of his time, and an example of all that is admirable about working-class families in 20th-century Glasgow and Liverpool, but it also means he is hardwired not to speak about his own vulnerabilities. The film ripples with the humour and happy intimacy of family life – despite Dalglish being torn apart on the inside and covered in a rash on the outside. He was not easy to live with during those dark days but the strength of his marriage to Marina seems obvious. Surely they spoke about his feelings after Hillsborough?

“No. We spoke more about the families and what they were going through. We wouldn’t speak about ourselves.”

Kenny Dalglish, whose son was on the Hillsbrough terraces, and Brian Clough after the abandonment of the Liverpool v Nottingham Forest FA Cup semi-final in April 1989. Photograph: Bob Thomas/Getty Images

Yet they remembered their worry that Paul might be one of those crushed and suffocated at Hillsborough. How long did Dalglish fear the worst for Paul? Fifteen minutes? “A wee bit longer than that,” he says softly. “But I knew he was OK before I made that announcement [when Dalglish addressed the Hillsborough crowd]. That was before four o’clock because I remember walking through the kitchens and the radio was giving the half-time scores. The trouble started at six minutes past three … so I was worried about Paul for more than half an hour. He was with the Liverpool supporters and had walked through the Leppings Lane end. I saw him in the tunnel and all you heard was me saying: ‘There he is!’”

That moment must have been one of surging relief? “Yeah, but I was lucky I had that moment. Many people did not have that good fortune.”

The wounds were ripped open again by the lies told by the Sun and the police. Dalglish emits a bleak, incredulous sound. “It was unbelievable. We saw how the Liverpool fans went to help people who were suffering. Ripping up advertising boards to use as stretchers, trying to care for them on the ground. How could others have lied? It was unimaginable.”

He has spoken of his gratitude that many of the families have found, in his word, “closure”, now justice has finally been done. Have Dalglish and his family reached their own closure?

“I don’t know what closure would be for us,” he says. “As long as we’re living we will support the families. So … we wouldn’t have a closure. I wouldn’t have a closure. At least the families have been totally exonerated. The families have been punished doubly by losing their loved ones and by spending the rest of their lives trying to get justice and solace.”

Dalglish’s life has also been tarnished by loss and hurt. Yet, as he and the film convey, it has been lit by happiness and glory. Watching Kenny is a reminder of his greatness as a footballer. He played with such skill and intelligence it’s hard to think of many better players in the history of British football. The dazzling vision and goals he scored illustrate why George Best insisted Dalglish would always be the first player he picked. “For me,” Dalglish says, “the best footage in the film is the private family footage. That’s more important than the football. I’ve seen the football. I know what happens.”

Kenny Dalglish, as Liverpool player-manager, and Ian Rush with the FA Cup after sealing the Double by beating Everton 3-1 in May 1986. Photograph: Bob Thomas/Getty Images

It’s still a remarkable story of how a Rangers supporter crossed the divide to play for Celtic where, Dalglish believes, “I could not have got a better education in football. Big Jock [Stein] was an encyclopaedia of football – not just facts and figures but of how and where to play. We all loved the ball at Celtic.”

That education was deepened at Liverpool and Dalglish recalls the managers he venerated – with Bill Shankly, Bob Paisley and Joe Fagan preceding him in a stately line. His own first managerial task was to lay a wreath at Liverpool’s Catholic Cathedral for all those who died at Heysel. Before the game a group of Liverpool’s supporters had charged at the Juventus fans – and, in the horrendous crush as a wall collapsed, most of the victims were Italian. Did he felt the weight of his role immediately, aged 34? “No. It was my responsibility. I wanted to do it.”

Dalglish had also been at Ibrox, as a Celtic junior, on the night of a different tragedy when 66 people died in a crush on a stairway as they tried to leave an Old Firm match in 1971. He withstood such adversity, at much personal cost, but the loneliness of management must have been as hard from the start? “No – at the outset it was brilliant. I was well-protected. Peter Robinson [Liverpool’s chief executive at the time] was the best administrator football has seen. Old Bob was upstairs if I needed help and I had Ronnie Moran and Roy Evans in the boot room. It didn’t seem lonely at first.”

Kenny Dalglish takes on Rangers’ John Greig during the 1974 Drybrough Cup final, won by Celtic in a penalty shootout. Photograph: Colorsport/Rex/Shutterstock

Eventually, Hillsborough took its toll and he resigned in February 1991, after a chaotic 4-4 draw with Everton when he felt unable to make any more decisions. Before then he had been successful and resilient – winning the Double in his first season in charge. “Alan Hansen said it was the worst Liverpool team he played in. He was part of it so he made a great contribution [Dalglish laughs]. We’d been in the European Cup final in May 1985 and this was the ’85-86 season. People think there was very little change but Craig Johnston and Jan Molby played more regularly. We signed Steve McMahon, and Alan Kennedy and Phil Neal were replaced by two young full‑backs in Stevie Nicol and Jim Beglin. It was a testing experience for everyone after Heysel but it felt seamless because there was no shouting or bawling. We didn’t do too badly.”

Dalglish created a more thrilling side when, after the sale of Ian Rush to Juventus, “we signed John Aldridge in the January [of 1987] and John Barnes and Peter Beardsley in the summer. I had an idea the chemistry would be good between me, Peter and Aldo … while Barnsey seemed the logical choice to feed goals to Aldo. Then we signed Ray Houghton who’d played with Aldo at Oxford. I tried my best to put together a team that looked good on paper but we had to prove it on the pitch – and they were different class.

“People talk about us beating Nottingham Forest 5-0 as the best but I’ve not got a league table of performances. There was a 4-0 game against QPR when they were top of the table. They came to Anfield early on in the season and, Jesus, Barnsey scored a couple of amazing goals. That wasn’t bad – but beating Forest 5-0 had to be a great performance. Whether it was the best is open to conjecture.”

Dalglish smiles – as he does when remembering his success in managing Blackburn to the Premier League title in 1994-95. “Blackburn was a fairytale. That was romantic. When I was approached to become manager, they were second bottom of what we call the Championship now. I had a few discussions with people there. In the meantime Tony Parks had been caretaker manager and he took them up to mid-table. I thought: ‘Well done, Tony [Dalglish laughs again]. Brilliant. That makes it a wee bit easier.’ I thought I’d have a go on the premise Tony stayed. I also brought in Ray Harford – brilliant feller and a brilliant coach. At the end of the first year we went up through the play‑offs, beating Leicester 1-0. We then signed [Alan] Shearer and were away. Finished fourth, then second, then champions.”

Kenny Dalglish with Tony Parkes, left, and Ray Harford after Blackburn won the title at Anfield in May 1995. Photograph: Shaun Botterill/Getty Images

His humour is evident again even when remembering how he lost his father at Blackburn. “My dad died on a Saturday, watching the scores come through. I think we won as well [Dalglish chuckles]. It was a good way to go.”

Does he miss being a manager? “It’s fantastic working with the players but the demands now, especially from the media, are intense. It’s understandable because when you look at the money being ploughed in you’ve got to pay some penance for that.”

The bond between players and fans has also diminished. “The biggest factor is cameraphones. Players aren’t allowed to be themselves. As soon as they’re out someone takes a picture. It’s changed from when we had the freedom to enjoy ourselves – and only the manager gave you a bollocking for drinking. Look at social media now. Someone takes a picture and they might not post it for four days or four weeks. But when they do post it people assume it’s live. So footballers are frightened of trying to be normal now. They’re terrified of fabrication.”

Is he hopeful that, in the next few years, Liverpool, now under Jürgen Klopp, might win the league for the first time since they lifted their third title under Dalglish in 1990 – with their last trophy being the League Cup won during his second tenure in 2012? “How long it takes them to win the league again is less important than the fact we have the right guy without a doubt. He’s going to give us the best possible chance to win the title.

“But this season Manchester City have been fantastic. You want your own team to be successful but that doesn’t mean you turn a blind eye to someone playing such entertaining football. City just hit you from everywhere. But as somebody said the other day you’re not competing against owners now. You’re competing against countries. Here’s a wee stat for you. When Man City played Liverpool they had a back five – which cost £210m. Kyle Walker was suspended. That’s another £50m. How can a football team, in three years, spend so much on a defence? We never even counted the new goalie. I don’t know what financial fair play is. Where are the restraints?”

Dalglish says all this without rancour – just in acknowledgement of how much football has changed. But in his own world, where his beloved Liverpool survived Heysel and Hillsborough under his compassionate watch, Dalglish remains constant and steady. “I’ve been lucky,” he says. “I played for Celtic and Liverpool with all those great players and managers. But they were very humble and kind. It seemed not a bad idea to follow their lead.”

Kenny is in cinemas now and available on DVD, Blu-ray and digital download from Monday