Mercedes' Andrew Shovlin has admitted it is "immensely satisfying" to defend both titles in 2018.
Lewis Hamilton won his fifth world championship and his second successive one of that in Mexico recently. The Mercedes team claimed their fourth successive constructors' in Brazil, too.
Ferrari challenged Mercedes more than people expected this season, with the Scuderia team possessing the quicker car in the early stages of the season and Shovlin believes it's been one of the toughest years for the Silver Arrows due to the challenge.
"A great result for the team," Shovlin said to The Checkered Flag. "We came here to win, so it's fantastic to have achieved that objective. It's been our toughest year for a long time, Ferrari pushed us hard in both championships and we've been running at 100% on both the chassis and engine sides almost since the word 'go', so it's a relief to get to the end and immensely satisfying that we've managed to hang onto both championships for another year.
"It was another great race from Lewis, he's not backed off one bit since winning the championship in Mexico and has worked as hard to win this race as every other race so well done on another deserved result."