Grevelius and Heinonen are Sweden's first winners and first finalists in either singles or doubles at the Stockholm Open since brothers Elias and Mikael Ymer took the doubles crown in 2016. It's a first ATP Tour victory for either player, both of whom are ranked outside the world's top 100.
The Swedes came through two three-set victories in the early rounds before seeing off Constantin Frantzen and Bart Stevens in straight sets in the semi-final. That set up a showdown with Mektic and Roger-Vasselin, which was made even more daunting given the first seeds won their last-four match without taking to the court, beating Adam Pavlasek and Patrik Rikl via a walkover.
However, it was the match sharpness of the outsiders that seemed to help early on, as they broke through on the Croatian and Frenchman's first service game en route to going 3-0 ahead. From then on, Grevelius and Heinonen held serve to take a 6-3 victory.
In the second set, the wildcards again took the first real chance that came their way, forcing a loss of serve with their first break point of the set in game five.
In game eight, they defended the only break point they faced before securing what, in the end, was a fairly comfortable win with their first and only match point, taking a 6-3, 6-4 victory in one hour and 18 minutes.
The pair, from Lidingo and Vaxjo, respectively, had won five Challenger Tour events together, but this marks the first ATP 250 tournament success for the duo.