Arbroath clinched the Ladbrokes League 2 title on Helicopter Saturday with a 1-1 draw away to Stirling Albion.
Martin Scott headed the Red Lichties into an early lead but Steven Doris missed a penalty before the break and the Binos equalised 16 minutes from time when Blair Henderson scored from the spot.
Forfar, who started the day just a point behind their local rivals, were beaten 4-2 by Annan Athletic at Station Park. That allowed Dick Campbell's men to celebrate with the trophy in front of 1,200 travelling fans in the Forthbank sunshine.
Forfar, Annan and Montrose will be in the promotion play-offs while bottom club Cowdenbeath face East Kilbride in a bid to retain their SPFL status.