Christian Horner fears the Monaco Grand Prix will be “left behind” unless drastic changes are made to Formula One’s most famous track – as rain saved another procession in the principality on Sunday.

Red Bull’s Max Verstappen led every lap to win for a second time in Monte Carlo, extending his championship lead to 39 points after six rounds.

Aston Martin driver Fernando Alonso took second place, with Alpine’s Esteban Ocon third. Lewis Hamilton and George Russell finished fourth and fifth respectively for Mercedes.

Sergio Perez, Verstappen’s closest title challenger, endured a horror show. He started last and finished 16th after five pit stops, and multiple collisions with different competitors, and the walls that wind their way round the two-mile course.

For 51 laps, the race was a dud. Verstappen saw off Alonso on the short run to Sainte Devote and the major players followed round one by one.

The rain enlivened the predictable spectacle. Carlos Sainz slid off and kissed the wall at Mirabeau in his Ferrari, while Russell and Perez made contact after the Mercedes man rejoined the track following an error, also at the rain-soaked Mirabeau corner.

Lance Stroll hit the barriers twice and Haas’ calamitous decision to keep Kevin Magnussen on slick tyres backfired as the Dane crunched the wall at Rascasse.

But take away the sodden race track, and the top dozen were on course to take the chequered flag in the order they started.

And even with the downpour, Verstappen, Alonso and Ocon, who started first, second and third, finished first, second and third.

“It was an exceptionally boring race until the rain came down,” was Russell’s damning verdict.

Red Bull team principal Horner, fresh from celebrating his team’s sixth win from as many races, picked up the debate.

“It’s Monaco and it’s here for its history and its uniqueness,” he said. “But the problem is that the cars are so big now.

“All venues have to evolve a little and if there was just one area where you could create space for an overtake it would just give that chance, because so much weight is placed on qualifying. The race is won or lost on Saturday.

“I am sure that with the creativeness there is and the amount of land they are reclaiming here, there’s got to be the opportunity to introduce a bigger braking zone.

“Maybe make Turn 1 a little sharper or slower, or extend the circuit if there is the opportunity to add in another kilometre that included a hairpin – that would be phenomenal.

“It’s something to contemplate because when you think of the next 20 years of Monaco you don’t want to see it left behind.

“It earns its place on the calendar. It’s the jewel in the crown in many respects, but as the sport continues to move forward you can’t stand still, and Monaco needs to be part of that process.”

Despite being considered among the most glamorous events in world sport, the Monaco track has remain largely unchanged from the first grand prix staged in 1929, and some have claimed it is no longer fit for purpose in its current guise.

F1 bosses have looked at ways to adapt the tight and twisty layout, but have made little progress.

Verstappen kept his composure in the changeable conditions, and even survived a bump with the wall when the rain landed at Portier, to take his 39th win for Red Bull, surpassing Sebastian Vettel’s record of 38 victories for the grid’s all-conquering team.

“If you have a good car you can break these numbers,” said Verstappen.

“I never thought I would be in this position in my career. Growing up, I wanted to be a Formula One driver and I am now winning these races. It is amazing and better than I could have ever imagined.”