Settled into the comfort of a luxurious Glasgow hotel, Martin O’Neill found himself wide awake on Tuesday night.

“Not a moment of sleep,” he confessed, reflecting on the eve of his remarkable return as Celtic’s interim manager as they prepared to face Falkirk.

“Just a day ago, I was casually enjoying a coffee near King’s Road in London, and now, suddenly, I’m back in the Celtic dugout against Falkirk. Questions raced through my mind: ‘What if we lose? What if the performance is lackluster? This could be a disaster.’ Honestly, it kept me up all night,” O’Neill admitted.

O’Neill’s approach was straightforward: “I told them to attack, grab the ball, and make things happen. Football doesn’t have to be complicated, especially with talented players like James Forrest, who has nimble feet.”

He encouraged his team with a timeless strategy: “Challenge your opponents, outmaneuver them, make it count. The art of dribbling past a defender is as old as the game itself. Is there anything wrong with that?”

Martin O’Neill had much to ponder this week after receiving the call to return to Celtic

O’Neill won his first game in charge and is now readying his side to face old foes Rangers in the League Cup semi-final

Senastian Tounekti celebrates making it 4-0 – and putting O’Neill’s sleepless night to bed

‘As the game unfolded, yes, I felt much better and I began to enjoy the occasion. Though I might not have known it hours earlier as the team trooped past me onto the bus from the hotel to the stadium. I stood there wishing them well and I think I knew about four of them. And half of them didn’t know me.’

This whole drama had started 48 hours earlier when Dermot Desmond offered O’Neill the job as interim boss. He then had to go and face the music he’s been facing for over 40 years now in football: his family. ‘I braced myself,’ said O’Neill.

Not least of his tasks was breaking the incredible news to his long-suffering wife, Geraldine, that he was being offered the chance to go back to Glasgow to manage Celtic. Oh, to have been a fly on the kitchen wall of that west London townhouse.

There was also the business of seeking advice from – or presenting the hard news to – his two daughters, Alana and Aisling, both successful in their own careers, whose opinions O’Neill has always sought. But, in whatever way they responded, O’Neill was always headed to Glasgow.

Yet he was still a bit unsure, which led to that sleepless night. O’Neill was asking himself: do I have the drive, the energy, the vitality to do this? Moreover, the game has changed so much over the past two decades since the period when O’Neill was in his performing prime on both sides of the border.

Was it madness to take Celtic on again? Shouldn’t he just stick to enjoyable – and comfy – punditry work?

‘My life was highly enjoyable: punditry work, my new book, some theatre conversations, and also being chairman of the League Managers Association,’ O’Neill told me. ‘The last is a role I don’t treat lightly, I’ve thrown myself into it. So I actually felt that I was quite busy.

‘But after my chat with Dermot, there was just this pull about Celtic. How do you resist it? I had great, great times at the club, though that was a long time ago. I keep saying it: it’s a quarter of a century ago now since I was first appointed Celtic manager. Despots and dictators have come and gone in that time. But here I am back.’

If O’Neill was to lead his side to victory over Rangers, there could be a clamour for him to stay

It was a whirlwind 48 hours for O’Neill as he decided to come back to Celtic 25 years after he was first appointed

Falkirk were dealt with – now for Rangers at Hampden tomorrow. In terms of O’Neill and Celtic and the future, so much rides on this game.

If O’Neill wins, and wins robustly, there will be a clamour for Celtic to suspend the whole chase for a new young manager – a Kieran McKenna type – and instead offer O’Neill an 18-month contract.

The tide will be unavoidable. The messiah has returned, and a win over Rangers will put a biblical tin lid on it all. O’Neill, gammy knee and all, will be walking on water.

He laughs at the scenario. ‘I don’t know, I really don’t. But what I do know is that Rangers will be formidable. Whatever has gone before, they are looking better and this is going to be one extraordinary test for us. But we will be at Hampden to try to win.’

Will it work? Can a man who has celebrated 50 years and more in the game possibly revive Celtic? We are about to find out. In one aspect, Desmond knows exactly what he is doing with Martin O’Neill.

He brings psychological power to Celtic. It was this quality that stood out more than any other during his first tour as manager between 2000 and 2005.

Time and again the force of O’Neill’s steely nature, radiating in front of his players across the pitch, hauled Celtic and their support to some momentous victories. One such was the remarkable 6-2 annihilation of Rangers in his opening month in office in 2000.

Another was the March 2003 UEFA Cup win over Liverpool at Anfield, when Neil Lennon said: ‘He spoke to us before that game and the hairs on the back of my neck were standing up. We were here with Martin O’Neill and we knew we were going to win. We strutted out onto Anfield that night.’

O’Neill had his fair share of success against Rangers in his first spell and now faces them in the second game of his second stint

O’Neill, with coach Gavin Strachan, still believes in a direct, simple style of play

O’Neill won three Premiership titles, three Scottish Cups and a League Cup in his first Celtic spell from 2000 to 2005

Time and again O’Neill, a two-time European Cup winner as a player with Brian Clough’s Nottingham Forest, gave Celtic strength just by being there.

In football they used to call it ‘presence’. On a sweltering evening he came so close to winning Celtic a European trophy against Jose Mourinho’s divers in Seville in 2003.

How will it all play out? Who knows? We’ve already seen what happened against Falkirk, now O’Neill moves on to Rangers in the Premier Sports Cup semi-final.

Two good wins under his belt and it will be a case of renewed messianic status. Defeat to Rangers, however, and O’Neill’s mindset may be changed. He will be the first to proclaim: ‘I want Celtic to get a new young manager in here as soon as possible.’

The most intriguing aspect in all of this is the question of whether O’Neill’s brand of football can still carry the day in 2025.

It sounds old-fashioned to say it but here is what he is about: teams who have a solid structure, maybe a 4-4-2 or a 4-3-3, who don’t complicate their game, don’t pass for passing sake, who aim to go forward with the ball – not backwards – and try to bring menace to the final third, in the air or on the ground, as often as possible.

Does this sound quaint? Because it’s not how Brendan Rodgers’ Celtic have been playing. O’Neill, in a short space of time, is attempting a paradigm-shift in Celtic’s style, to see what reward it can bring.

He will have his work cut out. Celtic face six fixtures in November, including two in Europe, of which five will be played away from Celtic Park. It is going to be a tough slog for O’Neill or whoever is in charge in these coming weeks. O’Neill has taken on an ominous task.

O’Neill, a two-time European Cup winner as a player with Brian Clough’s Nottingham Forest, gave Celtic strength just by being there in his first spell

On a sweltering evening in 2003 he came so close to winning Celtic a European trophy against Jose Mourinho’s divers

‘I don’t underestimate one bit what I’ve come into, not in the slightest,’ he told me

‘I don’t underestimate one bit what I’ve come into, not in the slightest,’ he said. ‘But you are in football to win, which means defending and attacking, and that part of it hasn’t changed.

‘I’ll say it until I’m blue in the face: Brian Clough was one of British football’s greatest ever managers but he made the game very, very simple. And he saw the game in very clear, simple terms.’

Dermot Desmond believes that O’Neill is the greatest Celtic manager since Jock Stein. He also knows that, in this period of Celtic turbulence, just having O’Neill back inside the building at Celtic Park will help bring assurance and composure to the stricken aircraft.

What glorious drama these days ahead promise to be. Full of event and incident. Perhaps the odd rammy. Bring on Sunday at Hampden.