Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @andrewffernando
Most Sri Lanka fast bowlers are lovers, not fighters. Sadly this is by process of elimination.
Look, quicks don't have to be angry. Chaminda Vaas rarely was. But many of the best, at least outside Sri Lanka, reserve the right to a stage persona. Andre Nel had a mountain man he called "Gunther". Dale Steyn has a vein on his forehead that seems to be made of concentrated fury. Vernon Philander will bowl a 125kph delivery, then stare at you like he has raised the smell of sulphur from the surface and brought demons up from the ground.
These are not the antics of the stereotypical Sri Lanka quick. The smile, the sigh, the arm around the shoulder of the team-mate who has dropped a catch, the loving caresses of the ball and the kiss before he lopes in to bowl - those are the island tropes.
Lahiru Kumara's delivery to dismiss Hashim Amla's was electric - the ball whizzing in late towards the batsman, beating the drive, making a small eruption of the stumps. But it was his reaction to the wicket that really drew the eye: a yell, a violent pumping of the fists, and shoulder action that - so abundant have injuries been lately - you were worried he would dislocate it.
He surged in after that first breakthrough. He hit 143kph in that same over, and once JP Duminy had been caught down the legside, hit 144kph in the next. On air, commentators had bemoaned the lack of skill from the visiting fast bowlers, and practically declared the attack toothless. Suddenly, with Kumara's introduction there was tension in the ground. Through the rest of the day, it was his spells that brought the Newlands crowd to attention.
He's only 19, so perhaps it's not surprising, but Kumara's first ever game of real domestic cricket had only been played in December. Perhaps that is just as well. The school system, from which he only recently graduated, retains a little of its own glory, but the first-class circuit is known to turn fast bowlers into husks. Of the top fifteen wicket-takers last season, only one was not a spinner. You can almost imagine Kumara going into a first-class season with his ox's shoulders and broad chest, and in the end emerging wimpy and 125kph, shorn of all his exuberance, dead in the eyes, and growing facial hair that looks like pubes.
Though Kumara is light on senior experience, he does have the benefit of having begun his cricket at a young age - moving to Trinity College for his cricket in Year 9. In comparison, Nuwan Pradeep only played leather-ball cricket from around the age of 20, and Suranga Lakmal had not started long before. Unlike them, Kumara has bowled fast right through his adolescence, which could make him less prone to injury, or so that theory goes.
He had four wickets in Zimbabwe before this match, but though he didn't remember the names of the batsmen he dismissed on those occasions, he says he will not forget his victims on this one.
"Of the three wickets today, I loved the one the Hashim Amla dismissal," he said after play. "He is one of the greatest players in the world and to get him with the way I did was a sweet feeling.
"I have three wickets now and maybe a chance for me to finish with a five wicket haul. Let's see how it goes. But the most important thing is to bowl them out as quickly as possible."
It does seem strange when it is a Sri Lankan fast bowler, not a spinner, or batsman that emerges. Fast bowling is the nation's cricket most faulty production line. At home they manage on dusty tracks, which sometimes even make the quicks completely superfluous, but on tours outside the continent they are like a car without an engine, with Angelo Mathews and his men sitting inside hoping no one notices that it is their own paddling feet that keep the body moving.
Maybe in years to come they will have better resources to call on. When Dushmantha Chameera eventually reaches his best, Sri Lanka hope to have a bowler of serious pace. Lahiru Kumara is not quite that quick, but today he swung the ball, and he did it with an attitude. For now, at 19, that is enough.