Activate discovery+Sep 23
It's D-Day across the continent this week with Chelsea among those requiring a miraculous turnaround to keep their European dreams alive.
Frank Lampard's Blues travel to the Allianz Arena tasked with overcoming a three-goal deficit against Bundesliga champions Bayern Munich.
BT Sport is showing every single game in the Champions League and Europa League and if last season's drama is anything to go by, fans are in store for plenty more twists and turns between now and the end of August.
After BT Sport's Club 2020 got underway with the Europa League on Wednesday and Thursday, Chelsea take centre stage on Saturday night with their match against Bayern getting underway from 7pm on BT Sport 1HD and Ultimate.
Ahead of that encounter, BT Sport remembers five tales of unlikely come-from-behind triumphs by British teams in Europe in years gone by.
2012: Chelsea 4-1 Napoli (5-4 on aggregate AET)
Chelsea have been here before.
Eight years ago the Blues were again heading for the Champions League exit door after Napoli had taken command of their last 16 tie with a 3-1 win in Naples.
But on a night that altered the destiny of the club, the Blues completed a dramatic performance to overcome the two-goal first-leg deficit and pave their way to glory in Munich two months later.
With Roberto Di Matteo in temporary charge following the sacking of Andre Villas-Boas, a tumultuous season at Stamford Bridge looked destined to end in more heartbreak until goals from Didier Drogba, John Terry, and Lampard sent the second leg to extra time.
Branislav Ivanovic struck a dramatic 105th-minute winner to send Chelsea through, sparking jubilant celebrations in south west London.
"I've had some great nights but I think this will go down in the club's history," said Di Matteo after the game.
Bayern away represents an all together sterner test for Chelsea this week, but Lampard has fond memories of Bavaria having captained the club to Champions League glory at the Allianz Arena later that year.
No team has overturned a 3-0 deficit when travelling away for the second leg but who would bet against it after last season's drama?
2016: Liverpool 4-3 Borussia Dortmund (5-4 on agg)
"That was football at its best."
In an epic game at the end of Jurgen Klopp's first season in charge at Anfield, Liverpool staged one of the most dramatic comebacks ever seen to overcome Borussia Dortmund and reach the Europa League semi-finals.
Although not strictly a second-leg comeback, Liverpool were down and out until the legendary atmosphere of the Kop helped haul their heroes home.
Four second-half goals against Borussia Dortmund saw Liverpool advance 5-4 on aggregate, a scenario that did not appear to be on the cards when the visitors went two goals up inside nine minutes, or when they scored a third in the second half to take a 3-1 lead.
On a poignant night that began with a tribute to the 96 supporters who died in the Hillsborough disaster 27 years earlier, what followed was a night that will live long in Liverpool folklore.
Klopp's side were twice left needing three goals to go through in the face of Dortmund's rapier attacks - but climbed the mountain twice with Dejan Lovren's injury-time header concluding a night packed with drama and emotion.
2019: Paris Saint-Germain 1-3 Manchester United (3-3* on agg)
"Ole's at the wheel!" BT Sport's Rio Ferdinand famously proclaimed on-air as Ole Gunnar Solskjaer's young Red Devils defied the odds to dump a star-studded PSG side out of the Champions League.
First-leg goals from Presnel Kimpembe and Kylian Mbappe left United with the unenviable task of overturning a two-goal deficit away from home, a feat that had never been achieved before.
A brace from Romelu Lukaku had put nerves on edge in the Parc des Princes but the hosts were still on course for a 3-2 aggregate win and a place in the quarter-finals.
But PSG's last-16 hoodoo struck again as Kimpembe was adjudged to have blocked Diogo Dalot's shot with his hand following a lengthy VAR consultation.
Up stepped an ice-cool Marcus Rashford to drill the penalty kick home and book United's place in the last eight of the Champions League.
The result left a bitter taste in Neymar's mouth. The Brazilian, who was watching on from the sidelines due to injury, tweeted: "It's a disgrace. Four guys who know nothing about football watch a slow-motion replay in front of the television."
2019 - Ajax 2-3 Tottenham Hotspur (3-3* on agg)
An unforgettable night that we all thought would never be matched for drama.
Trailing 1-0 from the first leg, Tottenham's task was made even more daunting as Ajax raced into a 2-0 lead in the return leg in Amsterdam.
After seeing off Juventus and Real Madrid to reach the semi-finals, Ajax's young guns looked on course for a place in the final at the Wanda Metropolitano.
By the end of the night Spurs manager Mauricio Pochettino was in tears - but for all the right reasons as the tie was turned on its head during four remarkable minutes.
Two Lucas Moura goals on the 55 and 59-minute mark silenced the Amsterdam Arena, levelling the scores on the night to leave Spurs requiring one goal to complete an against-the-odds comeback.
Deep into stoppage time, man of the moment Moura collected Dele Alli's through ball in his stride before sweeping the ball past Ajax keeper Andre Onana to seal the tie on away goals and spark pandamonium on the touchline.
Ajax's crestfallen stars sunk to their knees as Pochettino dropped to his with tears of joy his eyes.
2019: Liverpool 4-0 Barcelona (4-3 on agg)
This frankly ridiculous match will live long in the memory.
In the first leg, a Lionel Messi masterclass had left Liverpool's hopes of a second successive Champions League final dangling by a thread.
Klopp's troops had fought valiantly at the Nou Camp but Luis Suarez and two moments of magic from Messi looked to have ended Liverpool's dreams of redemption after losing to Barca's rivals Real Madrid in the 2018 showpiece.
With two-thirds of their famous front three missing - in the form of the injured Mohamed Salah and Roberto Firmino - even the most optimistic Liverpool fan would not have held out much hope ahead of the return leg at Anfield.
But when Divock Origi side-footed home from short range in the seventh-minute, a wave of cautious hope rippled around Anfield. Something special was about to happen.
Liverpool had to wait until the second half for another breakthrough as Georginio Wijnaldum struck twice in two minutes to leave the hosts on the cusp on the most unimaginable feat.
Roared on by the Kop, Liverpool sealed their most famous victory in recent years 11 minutes from time, when Trent Alexander-Arnold caught Barcelona napping with a quick corner, sweeping the ball to an unmarked Origi to convert for his second and Liverpool's all-important fourth goal.
Watch every Champions League and Europa League match exclusively live on BT Sport this August as Club 2020 takes over!