The 2018 Formula One championship is slipping away from Sebastian Vettel.

Lewis Hamilton's win at the Singapore Grand Prix on Sunday saw him strengthen his grip on the lead of the title battle, with a healthy 40 points in hand over his main rival. With just six races to go, it is a considerable margin: one grand prix victory alone is worth 25 points. so he is effectively a win and a third-place finish ahead of Vettel. It is a lead so healthy that, if Vettel were to win each of the remaining races ahead of Hamilton, the Ferrari driver would only claim the championship by two points.

The result of the Russian Grand Prix could swing Vettel's destiny out of his own hands.

If Hamilton finishes ahead of the Ferrari driver in Sochi then he would not need to win again to claim the championship crown. That might not seem significant, but since his victory at the French Grand Prix in June, Hamilton has not finished lower than second, while just two of his finishes this year have been outside of the podium positions. It's been done before: Nico Rosberg wrapped up his 2016 championship by finishing behind Hamilton at the final four races of that campaign, safe in the knowledge it was all he needed to do to win the title.

With Red Bull unlikely to replicate its Singapore pace at the remaining races, and Valtteri Bottas and Kimi Raikkonen unlikely to play anything other than supporting roles to their teammates for the rest of the season, it's not difficult to imagine Hamilton being able to continue that run -- assuming he avoids reliability issues or any in-race incidents.

Lewis Hamilton and Sebastian Vettel shake hands after the Singapore Grand Prix. Lars Baron/Getty Images

If the reigning world champion is victorious at both races in the upcoming double-header of Russia and Japan, he would only need to finish on the podium at two of the remaining four races to be the 2018 world champion. If Vettel is not able to cut the gap it increases the likelihood Hamilton could wrap up the championship before the finale in Abu Dhabi.

A race retirement for Hamilton would change the entire complexion of the championship fight, of course, giving Vettel the chance to slash 25 points from the deficit. However, since both its cars retired from the Austrian Grand Prix on July 1, Mercedes has redoubled its efforts in the reliability department and has looked almost bulletproof in the races since.

History suggests Ferrari has picked a bad time to hit a poor spell of form. In recent seasons, Hamilton has been at his best at the tail-end of the season. He also has some of his strongest venues coming up -- he has won five of the six U.S. Grands Prix held at Austin's Circuit of the Americas since it joined the calendar in 2012, as well as three of the last four races in Japan.

Mercedes has the lead -- 452 points to 415 -- and the momentum in the constructors' championship too. The Silver Arrows have outscored their red rivals at each of the five races since Ferrari waltzed away from July's British Grand Prix -- held at the Silverstone circuit, just down the road from Mercedes' F1 bases -- with the lead of both championships.