The last time Hearts went to Celtic Park prior to Saturday, in the dark depths of December, it represented perhaps the nadir of the season for Brendan Rodgers and his men. Even Santa was booed at half time, for pity’s sake.

Fast forward to a mild May afternoon at the weekend and the mood music around the stadium could hardly have been any more different. The performance from the men in green and white was also night and day compared to that tame festive defeat.

Now, finally, everyone at Celtic seems to be singing off the same hymn sheet, and Joe Hart – outstanding again on Saturday as he winds down his professional career – has been struck by the turnaround in both the fortunes of his team and the synergy between the pitch and the stands.

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Despite moments of tetchiness and the odd spot of rancour this season, it appears that all is now forgiven as Celtic close in on the title. And if they deliver it, perhaps even jolly old Saint Nick will be welcomed back to join Hart for a victory lap.

“Obviously I didn’t want Santa getting booed that day, but we got booed and damn right,” Hart said.

“We didn’t perform well that day and Hearts put us to bed.

“But that happens sometimes, and it’s important that we’ve put ourselves in a good place at the right time.

“Saturday was the only game that mattered, we put everything into it and got the right result.

“I really enjoyed that on Saturday. The pitch was magnificent, the atmosphere, oh my God. It was a good game, I thought Hearts started well and we took a little while to build into it, but Kyogo (Furuhashi) scored magical goals and important times and we grew and grew.

“We then dominated, and it was a good day at the office.”

If the atmosphere at Celtic Park was charged for the visit of Hearts, it will be on a whole other level again when Rangers travel across the city on Saturday.

Philippe Clement’s men eventually got the job done against 10-man Kilmarnock at Ibrox yesterday to stay within three points of Celtic, but travelling to the home of their great rivals without any of their fans, and with the home support now united in such a manner, will be a massive test of their mettle.

“Yes, but that doesn’t come easily and it’s not a fluke,” Hart said.

“It’s down to hard work and the fans realising that we are in a battle and we’re putting it all on the line.

“We really appreciate them, and it was an amazing atmosphere to play in, but it can only be that if we perform and show we are putting everything on the line.

“We were really united on Saturday, and I really enjoyed it.”

The goals at the weekend were greeted with roars of delight and relief, particularly the first two from Kyogo, which came when Hearts were still bang in an open and enjoyable contest.

But such was the mood in the stadium that every single positive for Celtic was acclaimed to the rafters. Whether that was the brilliant first half save that Hart made from Cammy Devlin, the lung-bursting recovery run from a revitalised Callum McGregor that denied Hearts an opportunity on the counter, or – Hart’s personal favourite – the return of Daizen Maeda from the substitute’s bench ahead of schedule.

For the keeper, that was a special moment, both for the reception he received and the significance of his presence for the team ahead of the Rangers game.

“Oh my,” he said. “It really was.

“We’re part of something, we’re together and united and we’ve got a common goal. You can’t underestimate that feeling.

“I don’t know about Daizen because there’s ice running through his veins, but for me, it makes the hairs on the back of your neck stand up.

“I’m not going to lie. It was tough as a squad when we got the news [about Daizen’s injury] - we thought he was going to miss the season.

“It was innocuous, he finished the game [against Rangers]. We didn’t know how or when it had happened - it’s hard to know with Daizen because he doesn’t say much.

“But as a medical staff, as a team and as a person, we’ve got to give them credit. To be ready to not only play but to impact a game like that was quite special.”

It’s not only Maeda who appears to have timed his run well. Celtic, on the back of perhaps their most polished performance of the season, look in fine fettle ahead of the monumental match that awaits them at the end of the week.

Hart believes they have the right mix of guts and guile to ensure that it they who are celebrating with their fans once again come Saturday evening.

“Those are the two sides that we’ve got,” he said.

“We just need to keep building on them. We’ve got Daizen whose hamstring was supposedly hanging off the bone, but he looked like he had been shot out of a cannon when he came on [against Hearts].

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“James Forrest, oh my God what a player. What a player. Incredible talent, incredible person to come in and perform like that - perform like he does every day.

“Systems and how teams work and transfer windows are what they are, but you can’t buy quality like that, you can’t buy presence like that on the football field.

“I could mention every single player. We’re only building though. We don’t know yet. But we’ve got it all to play for and we’ve put ourselves in a good position.

“We’ve got a big week coming up.”