He then switched to two-mile steeplechases and remained unbeaten over the next three seasons to set a world record for a jumps horse of 19 consecutive wins.
Ridden by Barry Geraghty, he started favourite and finished third behind Barters Hill and Buveur d'Air (also trained by Henderson).
He was then sent to Ireland for the Grade 1 Champion INH Flat Race at Punchestown on 29 April and, ridden by K. Harrington, finished sixth of the thirteen runners behind Bellshill.
Three weeks after his Chepstow victory, Altior won at Ascot Racecourse beating Ch'Tibello by one and a quarter lengths despite making a bad mistake at the final flight of hurdles.
On 15 November Altior was moved up in class for the Grade 2 Sharp Novices' Hurdle at Cheltenham Racecourse and started the 2/1 favourite.
[8] On 26 December he won again, taking a novice hurdle at Kempton Park Racecourse by thirteen lengths from the Willie Mullins-trained Open Eagle.
[11] Two weeks later he started at odds of 2/7 when he was moved up in class for the Grade 1 Henry VIII Novices' Chase at Sandown Park.
[13] The Grade 2 Wayward Lad Novices' Chase at Kempton saw Altior, ridden by Fehily, start at odds of 1/9 against three opponents.
[16] Having won nine successive races, Altior returned to the Cheltenham Festival of 14 March 2017 and started the 1/4 favourite for the Arkle Challenge Trophy.
The best fancied of his opponents were Royal Caviar, Charbel, Forest Bihan (Lightning Novices' Chase) and Cloudy Dream.
After racing in second place, Altior was left in front when Charbel fell and the second last and stayed on well to win by six lengths from Cloudy Dream.
[18] In mid-November however this plan was scrapped when Altior developed a breathing problem which required surgery on his larynx and eliminated him from the Tingle Creek Chase.
[19] The trainer was forced to defend his conduct in the matter, having stated just two days previously that the horse was "totally on target" for the Tingle Creek and then announcing the breathing problem in his blog on the website of online betting firm Unibet.
His next start came in the Clarence House Chase at Ascot, he opposed two rivals, Fox Norton and Diego Du Charmil.
Racing behind Saint Calvados and then taking the lead after 3 out, he was briefly headed by Sceau Royal at the last before his trademark turn of speed took him clear to win by one and three quarter lengths from Politologue.
[2] In September 2021, Henderson announced that the eleven-year-old would not race again, but would be retired by his owners "while still at his peak, fit, sound and healthy and ready for a new career".