Spring

Roaring Lion began his second season by starting odds-on favourite for the Craven Stakes (a major trial race for the 2000 Guineas) over the Rowley Mile on 19 April. He proved no match for Masar, who won by nine lengths and lost second place on the line to the 16/1 outsider White Mocha. In the 2000 Guineas over the same course and distance sixteen days later he started a 14/1 outsider and came home fifth behind Saxon Warrior, Tip Two Win, Masar and Elarqam, beaten two and a half lengths by the winner. On 17 May the colt started 3/1 favourite for the Dante Stakes over ten and a half furlongs at York Racecourse against eight opponents including Mildenberger, White Mocha, Crossed Baton (Blue Riband Trial Stakes) and Wells Farhh Go (Acomb Stakes). He took the lead a furlong and a half from the finish and accelerated away from the field to win "readily" by four and a half lengths.^[10] After the race his trainer John Gosden said "I’d have been disappointed if he hadn’t won like this, he’s been training beautifully at home and he’s woken up since the Guineas. He’s mentally in the zone, and I expected a big performance".^[11]

Summer

On 3 June 2018 Roaring Lion was one of twelve colts to contest the 239th running of the Derby Stakes over one and a half miles at Epsom Racecourse and started the 6/1 second favourite behind Saxon Warrior. After racing towards the rear and turning into the straight in ninth place he moved up to challenge the leaders approaching the final furlong and finished third behind Masar and Dee Ex Bee. Gosden later explained "He was out on his feet in the last 150 yards... it was like a 1,500 metre runner going in a marathon".^[12] The Eclipse Stakes over ten furlongs at Sandown Park Racecourse on 7 July saw Roaring Lion matched against older horses in a seven-runner field which included Saxon Warrior, Happily, Hawkbill and Cliffs of Moher. After being restrained by Murphy in fifth place, Roaring Lion moved up on the outside in the straight and in the closing stages he engaged in a sustained struggle with Saxon Warrior. He crossed the line a neck in front but appeared to have slightly hampered his rival when hanging to the right in the finals strides. The racecourse stewards held an immediate inquiry, but allowed the result to stand.^[13] After the race Murphy, who received four-day suspension for "careless riding" on the winner, commented "I was on the best horse in the race, that’s the bottom line".^[14]

At York in August Roaring Lion started at 3/1 when he faced Saxon Warrior yet again in the International Stakes in an eight runner field which also included the Group 1 winners Poet's Word (the 8/5 favourite), Thunder Snow, Benbatl (Dubai Turf), Latrobe (Irish Derby) and Without Parole (St James's Palace Stakes). After tracking the leaders on the inside rail he gained valuable racing room when the field tracked right to race up the stands-side in the straight. He went to the front inside the last quarter mile, drew clear of his rivals and won by three and a quarter lengths from Poet's Word, with third place going to the 50/1 outsider Thundering Blue.^[15] Gosden said "I had a difficult spring with him and he wasn't enjoying it, but he's been getting better and better and this wasn't a fluke. He wasn't really with me at the time of the Craven and the Guineas but the Guineas put him right. He's a proper horse with a massive middle on him and he’s got stronger as the year’s gone on... the curve is upward all the way."^[16]

Autumn

Roaring Lion at the 2018 Breeders' Cup

The Irish Champion Stakes over ten furlongs at Leopardstown Racecourse on 15 September saw Roaring Lion start the 8/11 favourite ahead of his old rival Saxon Warrior in their sixth meeting. The other five runners were Rhododendron, Study of Man (Prix du Jockey Club), Verbal Dexterity (National Stakes), Deauville (Belmont Derby) and Athena (Belmont Oaks). Murphy held the colt up towards the rear before switching to the outside to make his challenge in the last quarter mile by which point Saxon Warrior had established a clear advantage. Roaring Lion produced a strong late run, caught Saxon Warrior in the final strides and won by a neck.^[17] Oisin Murphy, who had very little prior experience of top-class race-riding in Ireland said "Once he got rolling I was always going to get there but I had to really get after him. I haven’t much experience around Leopardstown. I was learning on the job. But I was on an exceptional horse".^[18]

Roaring Lion was aimed at one of the major races on British Champions' Day at Ascot on 20 October with his connections eventually opting drop the colt back in distance for the Queen Elizabeth II Stakes over one mile rather than contest the Champion Stakes. He started the 2/1 favourite ahead of Recoletos (Prix du Moulin) and Laurens while the other ten runners included Addeybb, Lord Glitters, Lightning Spear and Romanised. Racing on soft ground he settled in mid-division as Hay Gaman set the pace Roaring Lion began to make progress down the centre of the track in the last quarter mile, he gained the advantage from the outsider Century Dream inside the final furlong and held off the challenge of the Irish filly I Can Fly to win by a neck.^[19] Gosden said "He has proven his class and his guts to get there, but I think he was hating every second of running on that ground. You could see from his action and the way he was carrying himself. I would not work him on that ground".^[20] After the race it was announced that the colt would be retired to his owner's Tweenhills Stud in Gloucestershire at the end of the year.^[21]

For his final race, Roaring Lion was sent to the United States to contest the Breeders' Cup Classic on dirt at Churchill Downs on 3 November and started the 8/1 fifth choice in the betting. After racing in mid-division he dropped out of contention in the last half mile and finished tailed-off last of the fourteen runners.

At the 2018 Cartier Awards, Roaring Lion was named Champion Three-year-old Colt and European Horse of the Year.^[22] In the 2018 World's Best Racehorse Rankings Roaring Lion was rated the best three-year-old in the world and the fourth best horse of any age or sex.^[23]