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Draper had already ensured he will become Britain's top player in the ATP rankings by reaching the showpiece match in Germany with back-to-back wins over Americans Francis Tiafoe and Brandon Nakashima.

Former Wimbledon runner-up Berrettini took Sunday's opener in just 33 minutes, but Draper fought back in a near-hour-long second set as the momentum shifted.

Draper failed to convert two set points at 5-4 and the first of two in the tiebreak, but he never looked back after levelling things up.

A break in the seventh game was enough to take the decider as Draper triumphed 3-6 7-6 (7-5) 6-4, serving a huge ace – his 12th of the contest – on match point.

Draper will crack the world's top 30 after claiming his maiden title in his third ATP final, having previously lost to Adrian Mannarino at last year's Sofia Open and Jiri Lehecka at January's Adelaide Open.

He will also become his country's top male player at the age of 22 years and 269 days, making him the youngest British number one since Andy Murray in November 2009.