Can one ball justify a selection?
Adil Rashid's call-up at the start of the series against India provoked much debate and, in some quarters, significant anger. Then throughout the five matches he played a bit-part role - 87 overs in total - and not even that much at Lord's where he did not bat, bowl or take a catch.
He certainly had not done anything wrong. In a low-scoring win at Edgbaston his googly to trap Ishant Sharma lbw in the second innings was important. At Trent Bridge he had Virat Kohli caught at slip for 97. He also provided further ballast to England's hefty lower order. But the question remained. What was he really there for? The answer: that ball to KL Rahul.
It remained a reasonably long shot that India would chase down a world-record 464 on the final day at The Oval, but Rahul and Rishabh Pant had raised the possibility with a rollicking stand of 204 in 44 overs. Joe Root looked a little rattled - the series was securely in the bag, but conceding the final match in such a style would have been unwanted blot on the season and a major dampener to Alastair Cook's farewell.
The decision to return to James Anderson was an obvious one - it is what three generations of England captains have done with regularity. At the other end, however, was a brave call that not every England leader would have taken. At times it had been debatable how much Root trusted Rashid, for example he left most of the spin bowling at the Ageas Bowl to Moeen Ali, but this was a show of faith.
Root persisted with Rashid who had been regularly dispatched into the stands by Pant, but had just started to land the ball consistently in the rough outside leg. He worked on the theory that if Anderson could dry up an end, as he did so impressively, that shots would have to come against the legspinner. It's what makes Rashid so effective in one-day cricket.
Then, from round the wicket, he delivered the ball of his Test career and a rival to the beauty that castled Kohli in the ODI at Headingley shortly before his surprise recall.
He went very wide on the crease, found a length well outside leg stump, the ball dipped into the footmarks and then fizzed. Rahul, seeing it like a football on 149 and wanting to score rather than just pad the delivery away, which would have been the safe (but defensive) option, opened up his stance to aim a flick through the leg side. The ball spun across his body, past the bat and clipped the top of off stump.
Rahul's face wasn't quite like Mike Gatting's in 1993, but it wore a look of significant shock. Rashid, the man who had shunned red-ball cricket earlier this year, pumped his fists and was swamped by team-mates, including a relieved captain. In one ball, any notion of a famous India win had been snuffed out. Rashid would continue to claim Pant's wicket, caught at long-off in the manner of many of his one-day dismissals, before Anderson grabbed the spotlight, and ultimately the headlines.
However, Rashid could take great satisfaction from the role he played at the end. He was selected as a luxury item, benefitting from the number of allrounders England have, which meant it wasn't imperative he bowled anywhere near as much as a frontline spinner normally would, but in one ball he showed the value of wristspin.
Now what, though? He was probably on the plane to Sri Lanka for the Test series before that delivery. Can he be such a luxury in conditions where spin will dominate and runs could be precious? If he is to be used in the same way, England will probably have to field three spinners in their XI to allow Root to throw Rashid the ball only when the situation is right. You can't ask seam bowlers to do the same holding role that Anderson provided at The Oval in the stifling heat and humidity of Galle and Colombo (although Anderson would no doubt manage it).
If Rashid forges a lengthy Test career with the walk-on role he has had this season it would go down as one of the more unusual in history. The next few months might also show how serious he is about a long-term return to red-ball cricket. But, in this series, he was selected to provide a bit of magic when it was needed. And he delivered.