The Champions League clash between Chelsea and Barcelona in 2009 is one of the most memorable games in the competition's history. 

A 0-0 draw at the Nou Camp set up a mouth-watering semi-final second leg at Stamford Bridge, with the winner set to take on Manchester United in the final. 

Had Chelsea beaten Barca that night, it would have seen a repeat of the previous year's final in Moscow, one that the Blues lost on penalties to their Premier League rivals. 

And everything started well for the London club. Michael Essien smashed the hosts in front with a stunning volley from outside the box that crashed in off the crossbar after nine minutes.

The following 80 were perhaps the longest that a Chelsea crowd had ever seen. But after keeping the Spanish side at bay for over 90 minutes, Andres Iniesta scored deep into stoppage time.

Like Essien's goal, it was a moment of magic, as the midfielder hit a rising shot past Petr Cech and into the net, booking Barca's place in the Champions League final on away goals.

But the game wasn't remembered for those two beautiful goals. Instead, it was referee Tom Henning Ovrebo who stole the headlines, as a number of terrible decisions led to ugly scenes at full-time. 

Over the course of 90 minutes, Chelsea saw four big penalty appeals ignored. 

The first came after Florent Malouda went down inside the Barca box - but the referee gave a freekick just outside it.

The second came when Didier Drogba went down, claiming his shirt had been pulled by Eric Abidal, but this time Ovrebo waved play on. 

The third and strongest appeal came with 10 minutes left when Gerard Pique appeared to handle the ball under pressure from Nicolas Anelka, but once again, the referee did not point to the spot. 

Even after Iniesta's equaliser, Chelsea had one final claim turned down when Michael Ballack's volley hit Samuel Eto'o's arm. 

When Ovrebo turned away from that one, the Blues midfielder chased him back up the pitch, expressing fury at having another stone-wall spot kick not given. 

Unsurprisingly, after the final whistle, almost everyone associated with Chelsea turned their hostility to the referee, who did well to get off the pitch as quickly as possible. 

There was carnage on the sideline and Drogba was infamously caught on camera shouting that the game was "a f***ing disgrace" in the face of Ovrebo. 

Now, ahead of another clash between Chelsea and Barca, the infamous referee has revealed just how much he feared for his safety in 2009. 

"After the match I did not talk to any footballer. I left the field with dignity and went to the dressing room," Ovrebo told Marca, per the Daily Mail. 

"I remember that we had to change hotels as there were many hostile people against us. We had to take care of ourselves that day and the next."

If it's any consolation to Chelsea fans, he also did admit that the number of mistakes he made that night may have cost the London club a place in the Champions League final.

"It was not my best day, really. But those mistakes can be committed by a referee. Some days you're not at the level you should be. I can't be proud of that performance. 

"I was responsible for the decisions that were made and we can argue that, if I had taken others, maybe Chelsea would have qualified for the final."

Both teams will want to avoid any similar controversy when they meet again on Tuesday.

And with so much talent on show at Stamford Bridge, the match could be one of the best seen so far in this season's competition.  

Would Chelsea have won the Champions League in 2009 if they had reached the final? Have YOUR say in the comments below.