In a 127-year history there are only two managers who have delivered a Treble at Celtic; Jock Stein and Martin O’Neill. Equally, there are only three men who know what it is like to captain Celtic to that feat – Billy McNeill, Paul Lambert and Tom Boyd.

The latter, firmly in the winter of his playing career, lifted the trophies with Lambert but it was the current Wolves manager who was pivotal to the most recent domestic sweep.

“It is quite incredible when you consider that,” reflected Lambert. “You do forget just how rare it is to achieve it. But then, the reason it is so rare for teams to do it is because how difficult it is.”

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Brendan Rodgers is the next manager who will aim to put himself in such exalted company.

Celtic, domestically, have looked capable of slaying all before them this term and there has been a level of panache and assurance as they have swashbuckled their way into a ten-point lead at the top of the table.

Inverness have claimed two points from them, the draw in the Highlands coming on the back of an exacting defeat in the Nou Camp to Barcelona.

The evidence this season is that Celtic look capable of dominating domestically in a way they haven’t for 15 years.

“You need a lot of things, including a bit of luck,” said Lambert. “But when you have belief through winning games you get into the habit of expecting to win every time you step foot onto the pitch.

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“I do feel quite privileged to have been part of a Celtic team to have won everything that season, back in 2000-01.

“We knew how long it had been since any Celtic team had achieved it and I do think it was special. But we had a really good team too.

“We also had a manager who got the best out of every player he had available. I think everyone knows the respect I had for Martin [O’Neill]. He was an incredible manager and what he achieved on the back of a season that we had lost the league by 21 points was amazing.

“We had a really tight squad. We worked for everyone and we never knew when we were beat.

“The other thing too is that we were up against an incredibly strong Rangers team. They had the de Boers, they were still spending a lot of money and Dick Advocaat had great success at Ibrox.

“I think it shows you just how big an achievement it was for us to win all three trophies that season when you consider who were up against.

“The fact it hasn’t been done since tells you how tough it is.

“They are the strongest team in Scotland and they are playing well right now.”

While Celtic fans would eagerly lap up a domestic Treble – for all that the players and manager will sensibly pour cold water on any such chat at the minute – the real barometer of just where the club are heading lies in the exacting environment of the Champions League.

There is a plausible argument to say that simply qualifying for the group stages and banking the near-on £30m that this season’s involvement will bring into the club was success itself, given the fact that this time 12 months ago Celtic were toiling against Molde.

Still, once in there, the challenge is to hold their own. It has been a mixed bag so far with disappointment in Barcelona and at home to Borussia Monchengladbach but Group C was a group where some observers felt that Celtic might struggle to claim even a point.

They have taken two – one from the pulsating draw against Manchester City and one from the battling draw in Germany – although claiming another one will be a significant ask.

The next game is against Barcelona at Celtic Park next Wednesday night, with the Catalans still needing points to claim that leading spot in the table.

Lambert was part of the Hoops side who restored European credibility with the run to Seville in 2003 in the UEFA Cup final, as well as captaining Celtic the first time they ever made it into the Champions League group stage.

The former Scotland skipper, who won the Champions League with Borussia Dortmund, is well qualified to understand just how important European success is to the club.

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“They’ve done alright in Europe,” said Lambert. “It’s going to be hard for them to qualify, of course, but they got a really tough group.

“When you are in the Champions League you have to double your efforts from your domestic games. It’s a big step up.

“I was over in Germany when they played Gladbach, who are in a good team. They are mid-table in the Bundesliga but that’s a much stronger league than the Scottish Premiership.

“But Celtic fans will have seen progress in Europe, in the hardest group in the Champions League.”