London - Chelsea and Barcelona renew hostilities in the Champions League last 16 on Tuesday in what has become a European classic in five tempestuous meetings shrouded in controversy.
Here are five previous knockout ties between the English champions and Catalan giants in the Champions League.
RIVALDO LEADS REVIVAL
Chelsea's first foray into the quarter-finals in 2000 got off to a flying start as Gianfranco Zola and a Tore Andre Flo double put the hosts 3-0 up inside 38 minutes of the first leg.
However, Luis Figo grabbed a vital away goal after the break to set up a Barca second leg fightback.
Rivaldo and Figo struck before half-time at the Camp Nou to give Barca the advantage on away goals before Flo restored Chelsea's aggregate lead.
Pep Guardiola provided the cross from which Dani Garcia's header took the game to extra-time.
Rivaldo's penalty edged Barca ahead, having earlier missed from the spot, before Patrick Kluivert capped the comeback with Barca's fifth.
MOURINHO GETS FRISKY
The presence of former Barca assistant Jose Mourinho as Chelsea boss took the rivalry to new heights in 2005.
Mourinho was furious with Swedish referee Anders Frisk after he sent-off Didier Drogba with Chelsea leading 1-0 at the Camp Nou in the first leg.
Frisk retired from refereeing less than a month later, citing death threats.
Barca came back against the 10 men to win 2-1 on the night, but were blown away by another fast Chelsea start at the Bridge.
Eidur Gudjohnsen, Frank Lampard and Damien Duff put the Blues 3-0 up inside 20 minutes before Ronaldinho, firstly from the penalty spot, and then with a stunning outside of the foot strike from outside the box nudged Barca ahead on away goals.
However, John Terry's header 14 minutes from time won the tie, with this time Barca complaining of a foul on goalkeeper Victor Valdes by Ricardo Carvalho.
MESSI TIMES FOR CHELSEA
Lionel Messi started just one knockout game on Barca's run to winning the Champions League in 2006. Unfortunately, for Chelsea the Argentine was still decisive.
Asier del Horno saw red for hacking down an 18-year-old Messi before half-time in the first leg.
Barca made the man advantage count through a Terry own goal and Samuel Eto'o in a 2-1 win.
Ronaldinho then sealed the tie back at the Camp Nou before Lampard's late penalty.
CHELSEA PAY HEAVY PENALTY
The most controversial of all the clashes came in 2009 when Chelsea saw four strong penalty appeals waived away by Norwegian referee Tom Henning Ovrebo before being hit by a late sucker punch.
After a forgettable 0-0 draw at the Camp Nou, Chelsea went in front in spectacular fashion through Michael Essien's volley.
Three penalty claims then came and went, whilst Barca also had Eric Abidal sent-off.
But the 10 men got the goal that paved the way for Guardiola's men to win the treble when Andres Iniesta fired into the top corner three minutes into stoppage time.
Yet there was still time for Ovrebo to turn down final howls for a spot-kick when the ball struck Eto'o's arm, sparking fury from Chelsea players and fans.
TORRES' TIME TO SHINE
The English side got their revenge in Guardiola's final Champions League match as Barca boss three years later by upsetting the odds despite again going down to 10 men.
Drogba gave Chelsea a slender 1-0 lead to take to Catalonia and that didn't look like being enough when Terry saw red for kicking out at Alexis Sanchez before Sergio Busquets and Iniesta turned the tie around.
However, Ramires's wonderful chip hauled Chelsea back into the tie and they withstood wave upon wave of Barca attack after the break as Messi also hit the bar with a penalty.
And it was the unlikely figure of Fernando Torres who landed the final blow when he broke away for Chelsea's second in stoppage time to set up the Londoners' solitary Champions League triumph.