Fletcher improved from third after the ski jump to first following the cross-country ski, topping the podium in a time of 28:48.7minutes with eighth place sufficient for Lamy Chappuis.
The Frenchman entered the final event with a 72-point lead over Akito Watabe with there the slightest chance that he might toppled him given his inconsistent form of late.
After ranking 16th to Watabe’s ninth after the ski jump there was still hope he could surrender the Crystal Globe but Lamy Chappuis produced the second-best cross-country ski to make certain of it.
Watabe was the eighth fastest to rank seventh, one place ahead of Lamy Chappuis but remaining one place behind him in the overall rankings with 1238 points to the Frenchman’s total of 1306.
Norwegian Mikko Kokslien ended third overall with 1061 points after finishing second for the second successive time in Oslo while Taihei Kato took bronze for his first-ever World Cup podium finish.