Blunders by goalkeepers with reputations that rank them among Europe’s finest conspired to heighten the drama at Stamford Bridge. First a crashing error of positioning by Petr Cech lifted Liverpool. Then José Manuel Reina’s fateful fumble of a Didier Drogba flick invited Chelsea to seize the tie and this they did — the ultimate irony — substantially through the efforts of a man who would not even have been playing but for John Terry’s suspension.

That he, Alex, stepped out of defence to score his team’s crucial second goal with an irresistible free kick was characteristic of a great occasion. Liverpool did much to make it and to prolong the excitement until two minutes from the end, when Frank Lampard’s second goal let everyone pause and start to savour an event so intoxicating it numbed the mind.

It is, though, Chelsea who stride on to their fifth Champions League semi-final in six years. Deservedly. Whatever Liverpool, craftily arranged by Rafael Benítez to cater for the absence of Steven Gerrard, threw at them — and at times we wondered if this was almost literally to become a kitchen-sink drama — they hurled back.

It was — to use a Brazilian’s phrase — football for adults. With Brazilians to the fore: not just Alex but Fábio Aurélio, the Liverpool left back, who got the party going with a cute free kick. Even Lucas Leiva scored, with a deflected shot towards the end as once again the flames were fanned and a header from Dirk Kuyt kept the outcome in doubt almost to the final whistle. Now, on Tuesday week, Chelsea will visit Barcelona, old foes from the José Mourinho era who are to pit their mouthwatering technique against Chelsea’s awesome power. But for much of last night it looked possible that the Catalan club would be facing Liverpool instead.

Liverpool were level on aggregate through Aurélio’s enterprise and a Xabi Alonso penalty but still needed another goal to progress when Nicolas Anelka, the substitute with whom Guus Hiddink had replaced the bewildering Salomon Kalou, crossed and Drogba’s skilful glance induced Reina to divert the ball over the line.

When Alex, taking advantage of Jamie Carragher’s foul on Drogba, sent the ball raging past Reina in the 57th minute to level the scores, it seemed over. Until we remembered that Liverpool were involved. We should have known better than to write off Benítez’s men in the mood they had fashioned from the wreckage of the defeat away to Middlesbrough in February. In the five matches that followed, all won, Liverpool scored 16 goals, conceding one. And to lead 2-0 last night was an achievement in itself, a throwback to Istanbul, if insufficient.

Benítez should not be second-guessed over Gerrard. On the face of it, the pre-match issue had been devilishly tricky for him. Should he take a gamble on Gerrard or save the captain for the more realistic aspiration that is represented by the English title?

If Benítez erred on the side of patience, he was right. Liverpool have six Barclays Premier League matches left, but there is plenty of danger in Manchester United’s seven; the champions play three matches in seven days next month and Liverpool will want to have all their attacking options — including Gerrard, who also missed Saturday’s 4-0 win over Blackburn Rovers at Anfield because of a groin injury — ready to exploit any slip.

The surprising aspect was that Benítez replaced Gerrard with Lucas. From what we have seen of the young Brazilian, he is nothing if not a holding player, an obstacle to opponents’ attacks rather than a creative force behind his own team’s. Yet here he was roaming behind Fernando Torres.

Maybe the intention was to keep Michael Essien occupied so Yossi Benayoun, given Albert Riera’s starting position on the left, could drift inside and fashion opportunities — such as the one he made for Torres in the thirteenth minute. The Spain striker was confident enough to shoot with his left foot, but sliced the ball into the Matthew Harding Stand (lower tier, to be fair). How the Chelsea fans chortled.

But soon the smile left their faces. Lampard’s push on Kuyt gave Liverpool a free kick wide on their right, about 40 yards from a goal Cech left all but vacant. As the goalkeeper prepared to deal with a swirler to the far post — a reasonable assumption, recklessly applied — Aurélio whipped the ball inside the near. Now that was Brazilian. And Chelsea started to panic.

Branislav Ivanovic, the two-goal hero of Anfield, wrestled Alonso in the penalty area as a more orthodox free kick from Aurélio floated in and, although there were no discernible appeals, Luis Medina Cantalejo, the Spanish referee, awarded a penalty that Alonso smacked home.