 Complete the following phrase:  Hamilton describes his rivalry with Sebastian Vettel as his favourite, believing their battles helped bring them closer together. After three years of Mercedes domice from 2014 to 2016, Ferrari produced a car that was capable of fighting for the championship in 2017 and 2018. Vettel, who was then driving for Ferrari, enjoyed an early lead on points, but Mercedes and Hamilton fought back and ultimately won the championships in both seasons. While there were some on-track flash points, most notably the 