THEY say one can become used to anything.

"I'm institutionalised in the Glasgow way," said Neil Lennon, with a suitably festive smile that disguised the hard reality that his 12 years in the city have not only been marked by conspicuous success but also scarred by abuse, assaults and death threats.

The negative barely rated a mention as the Celtic manager spoke of his gratitude and pride at being part of an extraordinary era at the club.

It is 12 years since Lennon, signed from Leicester City for £6m, made his debut for Martin O'Neill's side at Dens Park. Today, he will stand in a dug-out at the same ground as the manager of the champions, the league leaders and a side contemplating a last-16 tie in the Champions League. He has come a long way.

"My first training session for Celtic was at Barrowfield at 11am," he said. "I remember they had to put the floodlights on. I thought: 'Where am I here?' But even in that time the club has come on. You just look at the facilities at Lennoxtown."

He was, though, immediately impressed by the quality of player with whom he was training, citing the likes of Henrik Larsson, Chris Sutton, Lubomir Moravcik and Paul Lambert as outstanding. "When you are at your own club and playing premier league, you are always thinking about the Man Uniteds and Arsenals. Then I come up here, train with these guys and think: 'Oh, this is a good team. This is pretty special'," he said.

The first season brought a treble and Lennon, of course, was part of the side that reached the UEFA Cup final in Seville in 2003. But it all began in a street in Dundee. "Dens Park holds a special place in my heart. Of course, it does. It was the first place I pulled on the Celtic strip," said Lennon. "It's a very traditional ground. There is a slant on the pitch and you feel like you are running down a hill sometimes. I remember the dressing room being very tight and compact – and totally different from the premier league grounds. I was used to that at Crewe – playing in tight grounds – and there was a great crowd that night. It also started to snow."

He recalled the precise details of the Celtic victory before reflecting on how his spell in Scotland has shaped him: "I don't know what I'd have settled for. I didn't really have any preconceived ideas. I never realised how well it was going to go."

He added: "When did I first think I might return to Dens as Celtic manager one day? Never. Twelve years is a lifetime in football and so much has happened – on and off the pitch."

Old Firm matches would figure heavily in his on-field highlights package. "I didn't realise the intensity and ferocity of it," he said. "My first one was the League Cup semi at Hampden and Martin said: 'It will be a blur for you'. It was. The first half just flew past. I can't remember much about it but the good thing was we had back-to-back Old Firm games. We played at home on the Sunday and after the first game I was much better prepared.

"You just can't match the ferocity and intensity of it. You won't get games like that anywhere else. But it's the whole package that comes with Celtic. The analysis every day and the toing and froing that comes with the club. And the winning mentality that you have to adapt to. You have to win every game here – and do it in a certain style.

"You don't get that challenge at many other places. I enjoy it. There are days I love it, days I hate it. It's like everything else in life, you have good and bad days. But an opportunity came about and I wanted to grab it with both hands."

Of life in the city, he said: "I'm institutionalised in the Glasgow way. My kid has grown up here, I have family. It's not too dissimilar from growing up in Northern Ireland, barring the Troubles. We have a similar sense of humour. A similar way of thinking about things and the same love of football. It's very intense."

The rise of Lennon as a manager has been marked by that tension, some of it highly personal. The confrontations with referees and the early doubts about his suitability for the job have slipped into the mist, with the Northern Irishman emerging as a substantial figure on the back of a title win and victories over Barcelona and Spartak Moscow in the Champions League.

"I'm very happy with how things have gone" said Lennon, before introducing his customary note of caution. "I know it can change very quickly. I'm mindful of that. You are always sitting on the edge and you try to cover all the bases. Again, that's part of the challenge – success is paramount in this job."

Lennon, who confirmed Celtic would travel to Spain in the January break, added: "I'm proud of what I have achieved but I'm not going to stop at that. There is so much more to challenge myself with. I want longevity in this job and that's something that you're not guaranteed."

The next 12 years will be more than interesting.