Everywhere Sri Lanka go now, their captains are asked the same question. "Those three big names in your top four, all over 35 - aren't they getting past it now?" Four months into his leadership, Angelo Mathews already trots out clichés about class being permanent. Perhaps after the old hands set the night alight at the Oval, those doubts will abate for a time. What Kumar Sangakkara, Mahela Jayawardene and Tillakaratne Dilshan have secured for Sri Lanka is not just two points on the table, but the mighty tide that has turned for them at world events. This time, though, there is little doubt their run began in the loss to New Zealand.

Somewhere during that searing Malinga spell in Cardiff, there was a spark, and Sri Lanka ignited. There is no other way to explain how a batting unit that succumbed for 138 on a decent pitch can scale a mountain so emphatically against the hosts a few days later. Having gone so deep, so many times, Sri Lanka understand tournament cricket. They know a clean sheet of wins or a trunk-full of form for this key man or that one do not mean so much as the feeling in their gut, and they have latched on to belief and wrestled it into their cricket.

In the last World Twenty20, Lahiru Thirimanne's scoop off Tim Southee to tie the first Super Eights match set the dressing room ablaze. Five years before that, Malinga's four in four was their World Cup elixir. They rarely appear likely victors coming in, but when the gears begin to turn, the group uncovers a spirit that eludes them outside of major competition, and the unlikely gems begin to cluster together. Nuwan Kulasekara is popular far beyond his talent at home, and having walloped his first fifty in a Sri Lanka win, a nation will swoon when they awake to the scorecard. A cleverer pinch-hitting innings is difficult to recall.

"If Kulasekara's promotion didn't work, I think the team would have been torn to shreds," Sangakkara said. "Angelo would have taken a lot of stick and criticism saying what was he doing and what were the coaches thinking. But when it does work it's fantastic. Decisions like that can go both ways. I thought it was really strong of Angelo and the coaching staff to have taken that position. It was easy for [Kulasekara] to come and try and hit every ball, but he batted sensibly through Powerplay and then accelerated right after."

It might have been easy to reason that a blazing start was the only route to success against one of the best attacks in the competition, but Sri Lanka's experienced batsmen banked on belief over desperation throughout their chase, rarely giving in to daring. The early overs were defined by care, at least after Kusal Perera had perished. Sangakkara and Dilshan exploited the poor balls on a true pitch, but gave respect when the bowling demanded it. James Anderson's first five overs went for 15 and they had only made 48 by the end of the mandatory Powerplay. Sri Lanka bat deeper now than they have for much of their ODI history and today they trusted the hitters in the middle would provide a late surge.

Jayawardene's innings was wrought from trust as well, but in himself. In the 2011 World Cup he spoke of the belief his semi-final hundred four years earlier had bestowed - that he was a big-game, high-pressure performer. He might not have pleasant memories about the outcome of that final, but his innings in it was perhaps the best in the tournament. At the Oval, he defied a bouncy pitch and a sharp attack with the reverse-sweeps and swivel-pulls that are the foundation of his limited-overs batting, but are not always an advisable path to prosperity in English conditions. His innings proved a busy link between Sri Lanka's base and their final flourish.

Sangakkara was unwilling to label this one his best ODI knock, but for a man who does not always play his big innings in Sri Lanka wins, his second-highest one-day score must rank among the sweetest. Under pressure from the first ball, he undid England with nerveless, chanceless calculation. Jayawardene breathes cricket, but Sangakkara thinks it better than most who have played the game. At times he scored at a manic rate, and occasionally he played uncharacteristic strokes, yet nothing in his innings seemed rushed or improvised. A meticulous man of method, and now the first Sri Lankan batsman who might finish his ODI career with an average over 40, he eased the top order's burden early on, and engineered a shift in the tone of the match.

"It was really important for us to take momentum going back into the dressing room, but I think Bopara really managed to put some extra pressure on us by scoring 28 of the last over," Sangakkara said. "What would have been 270 suddenly became 293, and that's a big margin. But it's a do‑or‑die situation, so everyone was probably pretty pumped up to try and go and win the game.

"I think Angie brought us together just before we walked off the field and said, 'You know, it's do or die. Someone step up or everyone step up and try and win the game.' Whether through luck or ability, whatever, we managed to get through."

If Sri Lanka win their final group match against Australia on Monday, they will progress to the semi-final regardless of outcome of the other game. Sri Lanka have built a win out of belief at the Oval, and an embattled Australia have some way to go if they are to deny them another one.

Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. He tweets here