Serena Williams fought back from the brink of a shock defeat to stay on course for a third Wimbledon title with victory over Elena Dementieva in the longest women's semi-final in history.
The 27-year-old American was forced to produce all her battling qualities to overcome a spirited Dementieva, who produced a brilliant performance but still bowed out at the last-four stage for the second year in a row.
Williams saved a match point in the second set before forcing a decider and winning 6-7 (7/4) 7-5 8-6 in an epic duel on Centre Court that lasted 12 minutes short of three hours.
"It was really tough," Williams said. "She's been playing so well and has won a lot of matches against me in the past.
"I was not on my best game but my family were so positive. Elena played so well and we gave the crowd a wonderful match."
Father Richard Williams doffed his cap and both players left to a standing ovation but it was Dementieva who earned the biggest cheers and the sympathy of the crowd after pushing the two-time champion all the way in a memorable match.
The world number four, yet to win a grand slam title, was given little chance of halting Williams' serene march yet she produced a sublime performance that belied her record in big matches.
There was no obvious weakness in Dementieva's game and, for most of the match, she kept her suspect temperament in check.
She kept her trademark errors on serve to a minimum, underlined her status as arguably the best returner in the women's game and demonstrated a resolve not to be out-hit in the baseline rallies.
Williams began in ominous fashion with an ace, her 41st of the Championships, but the Russian produced a crashing forehand to earn a break point and followed it up with a sweet backhand down the line to draw first blood.
However, Dementieva failed to make the most of her flying start, allowing her opponent to break back immediately, and Williams was not threatened again on her serve in the opening set, which went to a tie-break.
Williams put a forehand wide to give Dementieva the first mini break and the Russian pounced on a weak second serve to move into a 6-3 lead.
A double fault, the one weakness in Dementieva's game this Wimbledon, threatened to undo the good work but Williams' accuracy on her forehand once more deserted her to hand the tie-break to the Russian with a 7-4 score.
The big question was whether Dementieva could maintain her high standard and doubts began to surface in the opening game of the second set when the accuracy of her groundstrokes deserted her.
Williams got the break and duly consolidated but Dementieva came up with a wonderful array of groundstrokes in the sixth game to break the American to love and get the set back on serve.
A 110mph second serve ace by the Russian averted the danger of another break and Williams was forced to dig deep to save two break points and avoid going 5-3 behind.
With the finishing sight in line, Dementieva began to show a sign of nerves and Williams achieved a crucial break to edge 6-5 ahead after successfully challenging a call on the sideline.
Serving for the second set, Williams suddenly found herself 15-40 down but was determined not to go out without a fight and came up with more aces to save two of four break points and a 12th ace of the match to secure the set at 7-5.
Dementieva had the advantage of serving first in the deciding set and it ought to have paid dividends.
A rare double fault by Williams gave her a break point in the fourth game and the American netted a forehand to go 3-1 behind.
However, the Russian demonstrated further jitters with three unforced errors to hand the break back.
Frequent glances towards her mother and coach Vera, who cast an emotional figure in the players' box, would have done little for her composure but a love service game did wonders to restore her flagging confidence.
Amid growing tension, Williams faltered on her serve and saved match point with a brave volley at the net.
It was by now the longest women's semi-final in Wimbledon history and the tennis just got better, with Dementieva twice falling to her knees in despair after losing out in epic rallies.
The crucial moment came in the 13th game when Dementieva failed to come from 15-40 behind on her serve and Williams served out for the victory.