The times on the speed gun kept on rising.
The first delivery was a relative loosener at 88.3 mph (142 kph). The next flashed up at 93.7 mph (151 kph). By the end of the over, Jofra Archer was firing down the red ball at 96.1 mph (155 kph).
Before long, England's newest cricket sensation was delivering a stinger that caused Australia superstar Steve Smith's left forearm to immediately swell up, and then flooring the same batsman — the best in the world — with a bumper that reared up and angled into the unprotected part of his neck.
Archer — lean, dreadlocked, and the owner of a menacing smile — is someone you might describe as a bar-emptier. He might only amble to the crease with a run-up that is quite short for a fast bowler, but then his deliveries explode onto batsmen with devastating pace and bounce.
Rarely can a test debut have had as big an impact as Archer's did at Lord's last week in the second match of the Ashes series between England and Australia. Some have compared it to Shane Warne's Ashes debut in 1993, when the Australia legspinner delivered the so-called "Ball of the Century" to flummox Mike Gatting.
Archer couldn't quite push England all the way to victory, with Australia hanging on gutsily for a draw as the light faded on a memorable Sunday evening at the home of cricket.
Yet he did more than just bowl the fastest over on record by an England player — at an average speed of 92.8 mph — and finish with overall figures of 5-91 off 44 overs.
With one of the most terrifying spells of pace bowling in a generation, the 24-year-old Archer potentially changed the course of this Ashes series. He also reignited the debate over concussion protocols and whether the helmets currently worn by batsmen offer enough protection in the face of a bowler of his venom.
"He makes things happen when not many others in world cricket can," said England captain Joe Root, relishing having this fierce new weapon in his bowling attack.
Ben Stokes went further.
"It was frightening," the England allrounder said. "The sky is the limit for that kid."
The Australians lead the series 1-0 with three tests remaining, but suddenly they have a rather large problem in the imposing Archer. At times, it felt as if their batsmen were cowering in the face of his hostility as balls flew past their faces.
On three occasions, the ball made contact with the head. Firstly, and most memorably, Smith took a 92 mph delivery by Archer on the side of his neck and slumped to the ground face-first. The impact was brutal. England allrounder Chris Woakes said he could "hear it was fleshy" despite fielding at fine leg.
Next in line was Marnus Labuschagne, who came into the team as a concussion substitute when Smith woke up groggy the morning after and was withdrawn from the test. Off the second ball he faced, Labuschagne was hit on the grille of his helmet by another vicious, sharply rising delivery from Archer. Labuschagne dropped to the ground and later required a new helmet.
Then there was Matthew Wade, who attempted to duck out of the way of a bouncer from Archer. The ball glanced off his helmet and ricocheted away for four leg byes.
"We've seen Jofra in Australia for a few years, we know the package he brings to the table," Australia captain Tim Paine said. "It's up to us as a team to formulate some plans."
Yet, with Smith potentially missing the third test in Leeds starting on Thursday as he recovers from a delayed concussion, Australia looks vulnerable.
Root said Archer has "really shaken things up" and acknowledged the quick might have the same kind of influence as Australia's Mitchell Johnson, whose pace helped him claim 37 wickets in the 2013-14 Ashes.
"He's added a different dynamic to our bowling group," Root said, "and has given Australia something different to think about."
The decision to allow Smith to resume his innings following concussion tests after being struck by Archer has been criticized, even though Cricket Australia defended the call of team doctor Richard Saw and urged against any over-reaction.
As for his return, the ICC's most recent review on concussion recommends a week away from action whereas CA guidelines rule out any return to physical activity for 24 hours, after which it must be a graduated process taken under constant review.
The incident has also brought into focus the effectiveness of the helmets widely used in cricket. Neck guards, which add an extra layer of protection to the head, were introduced following the death in 2014 of Smith's friend and teammate, Phil Hughes, as a result of being hit on the neck by a bouncer in a domestic match in Australia.
Players are recommended to wear the guards, but aren't forced to. Smith doesn't and is among those who feel they are uncomfortable.
"That is certainly something I need to have a look at," Smith said, "and perhaps try in the nets and see if I can find a way to get comfortable with it."
That would be advisable against Archer, who at one stage bowled 16 straight deliveries over 90 mph.
What a summer Archer is having. The Barbados-born player was fast-tracked into the England team in May for the recent Cricket World Cup under revised residency rules. He was the team's leading wicket-taker and helped England win the World Cup for the first time.
Now he's rousing England and its fans in the test arena.
"He's a seriously exciting talent," Stokes said. "He's announced himself on the world stage yet again."