When James Anderson defeated the defences of Ajinkya Rahane with a stunner on the final day of the Chennai Test, he went on top of the list for most wickets taken by a fast bowler after the age of 30. That wicket was Anderson's 342nd after turning 30, and he later added Rishabh Pant to that tally as well, to increase his lead over Courtney Walsh (341) on this list.
This should say a lot about Anderson's fitness levels, and his story is even more remarkable because of the improvement he's shown with his bowling in this period.
Anderson turned 30 on July 30, 2012. Since then, he has averaged 23.45 in 87 Tests. Among the 15 fast bowlers who have taken 150 or more wickets during this period, only three - Pat Cummins, Dale Steyn and Kagiso Rabada - have better averages. None of them, though, has taken even 60% of the number of wickets Anderson has taken in this period. In the 71 Tests Anderson played before turning 30, he averaged 30.37, which means his average has improved by almost 23% since he turned 30.
Befriending the older ball
When Anderson started out he was excellent with the new ball but with the older ball in hand, he wasn't quite as effective. In the 71 Tests he played before turning 30, he averaged 27.67 in the first 15 overs of an innings, but between overs 16 and 80, he conceded 34.54 runs per wicket.
Over the last eight-and-a-half years, though, the skillset has gradually expanded to include reverse swing, cutters, changes of length, pace and angle, and greater cricketing nous which comes with experience. Not only does he have a wider range of skills now, but also seems to have a much clearer idea of the execution.
The results are there for all to see. Since August 2012, Anderson's average in the first 15 overs has improved marginally - from 27.67 to 25.09 - but in the 16 to 80 overs range, the difference is stark: from 34.54, the average has dropped to 24.16, an improvement of 30%.
Among the 23 fast bowlers who have bowled at least 500 overs during this phase of an innings in this period, only three have better averages - the South African trio of Rabada, Steyn and Vernon Philander.
Overcoming the Asian challenge
For a bowler like Anderson, whose innate strength is the ability to swing the ball, doing well in Asia is a huge challenge. Before 2012, he played only five Tests in the continent, taking 12 wickets at 45.41. Then, in early 2012 - just before he turned 30 - he played back-to-back series in the UAE against Pakistan and in Sri Lanka. Though he didn't take a huge number of wickets - 18 in five Tests - he was giving little away: those 18 wickets came at an average of 24.72, and an economy rate of 2.46.
That was followed by a solid series in India, and though he had a lean time in Asia between 2016 and 2018, he has bounced back superbly this time around: he had a match haul of 6 for 46 in Galle, which was followed by 5 for 63 against India in Chennai. Since turning 30, Anderson concedes nearly nine fewer runs per wicket in Asia, compared to his numbers before he turned 30.
However, with Anderson, it's not only the wickets that matter; it's also the control he provides to the team with his ability to choke the run-flow: among the 13 non-Asian fast bowlers who have bowled at least 200 overs in Asia since the beginning of 2012, Anderson's economy rate of 2.4 is the best, marginally better than Philander's 2.5.
The extra bows in Anderson's armoury have been even more useful in Asia, as they have made him a threat even with the older ball, something that wasn't necessarily true in the early days of his career. Before he turned 30, Anderson averaged 47.77 runs per wicket between overs 16 and 80, and had a strike rate of 101 balls per wicket. Since then, the average has improved to 22.72. Nowhere was that improvement more evident than in the 27th over of India's second innings in Chennai, when those two wickets of Shubman Gill and Rahane decisively swung the game England's way.
However, his numbers in Australia haven't improved as dramatically - he averaged 35.79 in eight Tests there before turning 30, and 35.09 in ten Tests since then - but his last series there was pretty impressive: 17 wickets at 27.82, conceding just 2.11 runs per over.
The matchwinner
In the post-30 phase of Anderson's career, England have won 37 of 87 matches he has been part of, and in those 37 wins, Anderson has taken 170 wickets at a stunning average of 16.43. Among the 23 bowlers who have taken at least 75 wickets in wins during this period, no one has a better average. In defeats or draws, the average goes up to 30.36. His numbers in wins illustrate just how important Anderson is, even at 38, to England's Test fortunes.

S Rajesh is stats editor of ESPNcricinfo. @rajeshstats