The South African winger helped Edinburgh move closer to securing a Guinness PRO14 Final Series spot, bagging two of the hosts’ eight tries.
His electric pace was put to good use on both occasions, the first coming immediately after Blair Kinghorn opened the scoring inside six minutes.
Almost straight from the restart, Kinghorn fed van der Merwe again, who breezed past Tom Varndell before racing clear down the left to inflict more damage inside the opening 10 minutes.
Van der Merwe’s second came just after half time, following a great Edinburgh break from inside their own 22.
A darting run from scrum-half Sam Hidalgo-Clyne split the Scarlets defence before he put an inch-perfect grubber into the corner for van der Merwe to latch onto and cross the whitewash.
The winger also made a phenomenal 206 metres, exactly double the next-highest metre maker on the day, whilst winning three turnovers and beating seven defenders with five clean breaks.
Guinness PRO14 Final 2018 Ticket Information: Prices start at just €35 at www.ticketmaster.ie with tickets available to suit every experience.
To book hospitality visit: https://www.pro14rugby.org/hospitality
For Travel packages visit: https://www.pro14rugby.org/travel-packages
For Fanzone & Dublin 7s visit: http://www.dublin7sfestival.ie