Defending champion Marin Cilic flew through his opening match of the Fever-Tree Championships at Queen's Club with a 6-1 7-6 (7-5) victory over Christian Garin.
Cilic, who beat Novak Djokovic to take the title 12 months ago, raced through the first set in just 21 minutes before being met by a stronger challenge in the second.
The Croatian was pushed into a tie-break and went down by a mini-break before he regained his composure and secured victory.
Cilic, a two-time winner, holds a 30-9 win-loss record at Queen's Club and has reached the title-deciding match on two other occasions.
Diego Schwartzman will be the next man to challenge Cilic on Wednesday after he prevailed 6-2 6-3 over Alexander Bublik.
Russia's Daniil Medvedev also commenced his campaign in south-west London with a straight-sets 6-2 6-4 victory over Fernando Verdasco.
The world No 13 took just one hour and ten minutes to dispatch his opponent and ended a five-match losing streak in the process.
Kevin Anderson returned to action for the first time since March
The British No 2 Cameron Norrie put a stirring performance on court against South Africa's Kevin Anderson before being beaten 4-6 7-6 (7-5) 6-4.
Anderson's presence at Queen's Club marked his first outing since March due to a lingering elbow injury and it took him awhile to find the required level of match sharpness.
Norrie broke his opponent in the first game and confidently secured the first set. However, last year's Wimbledon finalist took the second to a tie-break and then used his powerful serve to convert a third set-point.
The South African's break of the Norrie serve arrived early in the decider and he quickly cemented it to go 4-2 up and finished the job from there.
Anderson will face France's Gilles Simon after he triumphed in a final-set tie-break against Britain's James Ward.
Ward, like Norrie, secured the first set before dropping the second.
The Brit, who is ranked 212 in the world, regrouped superbly. He put himself in the driving seat at 4-2 in the decider however, let it slip and ultimately lost the tie-break 7-2.
Nicolas Mahut, who reached the final at Queen's Club as a qualifier in 2007, arrived through that route once again and defeated Frances Tiafoe 6-3 7-6 (7-5).