The 26-year-old Bublik, who regularly delivered first serves at speeds of more than 220kph, gave his opponent no chance on his own serve to make his first final of the year as the grass season heads towards Wimbledon in just over a week.

Zverev, a two-time finalist in Halle, quickly dropped a break behind with Bublik racing to a 4-1 lead in the first set.

The German’s return was no match for the Kazakh’s thundering serve and Bublik quickly wrapped up the first set in 35 minutes.

Bublik, who reached his second tour semifinal of the season after Italian Jannik Sinner was forced to retire injured, had two more break chances at 3-3 but Zverev dug deep to stay in the contest.

However, the Kazakh played a flawless game at 5-5 to snatch the break he wanted with a superb crosscourt forehand winner and then served out the match.

The world No 48 will face either Roberto Bautista Agut of Spain or Russian Andrey Rublev in Sunday’s final.