This is why Adil Rashid is in the England team.
There have been moments in this series - not least in the second innings in Galle and Kandy - when Rashid has seemed a bit of a luxury item in this side. And it's true that, on turning wickets, where finger-spinners such as Moeen Ali and Jack Leach are able to gain assistance, there isn't much need for his wrist-spin.
In a perfect world, Rashid would have the control of Shane Warne. If he did, he would be able to play as the lone spinner and deliver a defensive and aggressive option for his captain.
But that's not realistic. Warne, for his control as much as the vast turn he achieved for much of his career, was a freak and the majority of other legspinners - especially those who give the ball a big tweak, rather than roll it out with minor variations such as Eric Hollies - cannot offer such a dual role. So on turning wickets, Moeen and Leach offer the threat without the four-balls that come with the territory of most legspinners.
But here in Colombo, conditions were a little different. Here, in Colombo, the finger-spinners had been played out with something approaching ease and, as Dimuth Karunaratne and Dhananjaya de Silva put together the largest partnership of the series (142), England were made to look a bit impotent.
But then Rashid was introduced into the attack. Suddenly, England had a bowler who was able to coax movement from the pitch and challenge the batsmen on both sides of the bat. They had a bowler who was performing with confidence, too, and who settled into such a good rhythm that he claimed all his five wickets in one spell of 12.5 overs.
His final figures - 5 for 49 - were not only Rashid's Test-best figures, they were the best from an England legspinner in almost 60 years. Since Tommy Greenhough took 5 for 35 against India at Lord's in 1959, in fact.
If the breakthrough wicket was largely the result of some exceptional fielding from Keaton Jennings - anticipating the likely direction of the ball, Jennings at short-leg stayed low and clung on to a sharp chance - it was also reward for Rashid's control. Maintaining a good length without many of the drag-downs that characterise his bowling on a bad day, he generally stuck to legbreaks, though Roshen Silva, who didn't read the googly well in Kandy, again failed to spot a wrong'un and edged to short leg.
There was, perhaps, a little anxiety in Sri Lanka's batting, too. Aware of Ben Foakes' excellence with the gloves and Jennings' excellence under the lid, they knew any mistake could be costly and looked less willing to leave their crease than might be expected. As a result, they allowed Rashid to settle into his natural length, bowl his natural pace (his entire spell was delivered between 47 and 54 mph) and rely on his variations and, most of all, his fine legbreak.
There had been shades of this earlier in the series. In Galle, for example, Angelo Mathews and Dinesh Chandimal appeared to be batting Sri Lanka into a position of some strength. There was nothing in the conditions for the seamers and England's two finger-spinners had been negated. But Rashid came on with a licence to attack and, before long, turned one past the advancing Chandimal's outside edge to have him stumped. He didn't gain many headlines, but it was a vital moment in the game.
This, then, is Rashid's role. No longer is he expected to provide a holding role; no longer is he being asked to bowl quicker in an attempt to tie down batsmen. Leach can perform that role. Rashid is simply asked to spin the ball sharply and try to take wickets. There will be days - quite a few of them, probably - when he goes at five-an-over and looks a luxury that England can do without. But there will also be days like this when he offers the key to unlocking line-ups that nobody else can match. If England are going to win in India, it will require their bowling to have far more bite than was the case on the last tour. Rashid, used in this way, suggests that may yet be possible.
Ben Stokes was almost as impressive. Stokes is, in many ways, the man who balances this team. Without him, it might be hard to find a way to include three spinners without compromising in other departments. And, without him, it would be hard to find a room for the attacking style bowler that gives England options they have lacked on previous overseas tours in recent years.
For any seamer to deliver a ten-over spell in these conditions - brutally hot and humid as they are - is impressive (albeit the first four overs were bowled before tea and the other six after); for that spell to include a barrage of energy sapping short balls is extraordinary.
But this is one of the many options Stokes offers his captains. He is the one man in the series to bowl in excess of 90 mph and the one man in the series to have brought any sense of intimidation into the game. While a couple of the wickets may look, in isolation, a little fortunate (Niroshan Dickwella, for example, was caught down the leg-side as he attempted to glance), they were the result of minds scrambled by the contrasting threats offered by Stokes and Rashid and, perhaps, ruffled by his aggression. To coax such life out of these pitches was remarkable. He has now claimed twice as many wickets - four - as the other three seamers England that have used in the series combined. In such form, he might offer England the pace they require to challenge in Australia.
That legspin / fast bowling combination precipitated such a collapse that Sri Lanka lost their last nine wickets for just 67 runs. England have been on the wrong end of such assaults many, many times. To see them inflict the damage in such style was to see a new team starting to blossom. A team that is working out its strengths and working out a way in win in different conditions. We all know that far tougher challenges lie ahead - to be considered a really good team, they probably need to win in India and Australia - but they are learning and improving all the time. And they are extremely entertaining. It will be fascinating to see where the next couple of years take them.
And then there's Jennings. It's not so long ago that Jennings was moved out of the cordon after dropping a succession of chances. He is not especially quick in the field, either, so there was some doubt over where he should be placed.
Not any more. His anticipation, his concentration, his reactions and, most of all, his courage at short-leg have been extraordinary. Put simply, both here and in Kandy, he has created chances that other fielders in the position could not have imagined. At times it looked as if he could catch Lord Lucan. Dhananjaya de Silva referred to him as "the man who turned the game around" while Rashid, who had the most reason to be grateful, referred to him as "exceptional". It's hard to disagree. His ability at short-leg has offered his side a new dimension in the field. These are early days, but he is making the sort of contribution to England that Jonty Rhodes once made for South Africa.
Stokes, Jennings and Rashid turned the day around for England. They had actually squandered an opportunity to make a really imposing first-innings total with some soft batting - Moeen Ali lofting to long-off was particularly painful - and it had looked as if they were chasing the game for their first 40 overs or so in the field.
Root should probably have introduced Stokes and Rashid earlier. After one speculative over (the 22nd), Rashid didn't bowl his second until the 42nd of the innings, while Stokes didn't come on until the 45th over. By then, Sri Lanka were 162 for 1. Bizarrely, Root had given himself two overs by that point. It is unthinkable he would bowl as much if he were not captain.
His use of Stokes seems somewhat one-dimensional, too. In this series, for example, Stokes has been used almost exclusively to test the batsmen with bouncers. That's a legitimate tactic and, both here and in Galle, Stokes has performed it admirably. But there is more to his game than that. On this pitch, with his pedigree as a swing bowler, he should probably have taken the new ball. By the time he came on, any hope of that had long since gone.
It actually wasn't a great start to the day for Root. He dropped a couple of relatively straightforward catches at first slip, too - both opening batsmen; both off the excellent Stuart Broad, who generated pace of 89.5 mph at one stage - and looked thoroughly disgusted with himself for the next couple of hours.
But Rashid, Stokes and Jennings helped lift the mood. England remain on track for a first whitewash (in series of three matches or more) in Asia and a first away anywhere since 1963. They are not the finished article, but there is much to like and admire about this team.