They left London in their thousands, full of hope and devotion, heading for Paris in the springtime, yet romantic anticipation lasted all of 18 minutes, which was when Arsenal’s goalkeeper, Jens Lehmann, was sent off in the 2006 Champions League final against Barcelona at the Stade de France.

Twenty years on, as Arsenal fans again travel in anticipation, this time to Budapest, for the club’s second Champions League final, you could argue that Arsenal hearts have been a little broken ever since.

On the surface, all looked promising in May 2006. Two years previously, the Invincibles of Patrick Vieira, Thierry Henry, Dennis Bergkamp and Robert Pires had made English football history, now Ashley Cole and Cesc Fàbregas were establishing themselves and Arsène Wenger’s knack of signing obscure talent continued with Kolo Touré, Robin van Persie and Gaël Clichy.

That August the club would move into the Emirates Stadium, a seismic upheaval from playing at Highbury, but one that theoretically allowed them to challenge Manchester United for the next 20 years. Now the club just had to take the final step and win the Champions League to consolidate their reputation as a global force.

The overwhelming memory of that day for those at the club at the time is profound frustration. “We were robbed,” says Keith Edelman, then managing director. “The ref shouldn’t have given him a red card.”

The referee, Terje Hauge, is said to have apologised to the Arsenal delegation, for he could easily have played an advantage as Ludovic Giuly scored from the loose ball from Lehmann’s collision with Samuel Eto’o. Arsenal would have been 1-0 down, but at least with 11 men.

That said, they were formidable thereafter, taking the lead through Sol Campbell and hanging on until 76 minutes when Eto’o scored, with Juliano Belletti getting the winner four minutes later.

Prescient fans might have had a sense of foreboding, that the Wenger era had peaked and was coming down the other side. Vieira had departed for Juventus the year before, leaving a huge void; Pires was playing his last match, a sad finale as he would be the sacrificial lamb, subbed when Manuel Almunia came on for Lehmann; Bergkamp was on the bench, also his last match. Henry would leave for Barcelona a year later.

The vice-chair, David Dein, had defined the coming decade and the forces that would blow Arsenal off course when he had said: “Roman Abramovich has parked his tanks on our lawn and is firing £50 notes.”

The new stadium was meant to consolidate the future, but it came just as the game’s finances became turbo-charged by the Russian oligarch’s arrival at Chelsea in 2003 and Sheikh Mansour’s at Manchester City in 2008. Even though a bond issue in 2006 had reduced interest payments on the stadium, the new ground initially made Arsenal uncompetitive.

“We didn’t have the luxury of funding; we were begging and borrowing to tread water,” says one Arsenal director of that time. “We had the albatross of the stadium around our neck, £400m of debt. We were strapped for cash and had to sell before we could buy and we were going through a transition with the Invincibles breaking up.”

“When I came in, the board said they wanted to build a stadium,” says Edelman, who joined in 2000. “So I said: ‘How much are you going to put in?’ And everyone looked at me blankly.”

The start-up cash was eventually raised in a £47m deal with the erstwhile media giant Granada for 10% of the club and 50% of the “internet rights”, a peak dotcom bubble deal. Granada had bought 50% of nothing. “It was an amazing deal,” Edelman says.

But their financial worries were not over. Banks were not keen on lending to football clubs in that era. “We had 10 banks [we pitched to] and all the credit committees said: ‘No,’” Edelman says. “That was an amazing moment. We couldn’t build the stadium.”

Eventually, the club persuaded Nike to pay £140m for a 10-year shirt deal and Emirates to pay £100m for a 10-year naming rights and shirt sponsorship deal, but the club were mortgaging future revenues to pay for now. Barclays also loaned £120m. “It was a white knuckle ride,” Edelman says.

Ultimately, Arsenal could not keep up and when the club quibbled over a £5,000-a-week difference over Cole’s contract he left for Chelsea that summer. City would take Touré and Clichy and later Samir Nasri and Emmanuel Adebayor. It was impossible to stem the bleeding and Wenger, who failed to win a trophy between 2005 and 2014, lost Van Persie to Manchester United and Fàbregas to Barcelona, the team who would dominate the era.

The roots of the Barça revival were evident in Paris, with Xavi Hernández and Andrés Iniesta on the bench, though another 18-year-old was sulkily refusing to join in celebrations because he did not make the squad. Just who did this precocious teen, Lionel Messi, think he was?

Meanwhile, football was moving on to an era of sporting directors and analytics. “Arsène couldn’t do all the transfers on his own without David,” says Edelman, who was often cast as Dein’s arch enemy at the time, but is clear it was the vice-chair’s acrimonious departure in 2007 that precipitated the stagnant years. That said, Edelman, who left in 2008, feels Arsenal could have recovered more quickly from the shock of the Abramovich era and never imagined there would be seven more trophyless years after Paris. “I felt the heavy lifting had been done on the stadium,” he says. “The fact that the board was at daggers drawn didn’t help matters.”

The desperation to bridge the funding gap created by Chelsea and City led to the fracture of the Arsenal board and it is forgotten by most that Dein, the less exalted straight man in a double act with Wenger that created the Invincibles, was fired for attempting to bring US money to the table, specifically Stan Kroenke. Once Dein was gone, the board magically saw the wisdom of his thinking and the path was paved for today’s Arsenal with Stan and his son Josh in charge.

Even so, the route back to the summit proved long and arduous. Fittingly, Mikel Arteta provided a significant staging post by lifting the FA Cup in 2014 as captain. Yet the pain of 2006 and the subsequent decline remains raw even 20 years on. Now, finally, Arteta can mend hearts broken in Paris.