#4 (t) Geoff Duke
British rider Geoff Duke was a prominent motorcycle racer in the 1950s. His career lasted 9 years, between 1950 and 1959. He won his first 500cc Riders Championship in 1951. In the same year, he also won the 300cc title. His first title came with Team Norton. He won a hat-trick of Championships at the 500cc level with Team Gilera from 1953-1955.
#4 (t) Marc Marquez
The Spaniard Marc Marquez nicknamed 'The Ant' is one of 3 drivers to have won the Riders Championship across all three classes. Marquez won his first MotoGP premier class Riders Championship with Team Repsol Honda in the year 2013 at the age of 20, the youngest to do so.
He defended his title in 2014, winning an astounding 10 races in a row. Marquez then won two more Championships in 2016 and 2017 and is well on course to win his 5th MotoGP Championship in the year 2018.