Alonso: Vandoorne gap shows I'm in best form

Vandoorne came into F1 full-time this year very highly-rated from a junior career that included a dominant 2015 GP2 title, and having made an impressive grand prix debut as the injured Alonso's stand-in in Bahrain last year.

But Vandoorne is yet to beat Alonso in qualifying, trailing him by 0.586 seconds on average in the first segment, and only made it out of Q1 in Monaco when teamed with Jenson Button.

For Alonso, this is further evidence that he is in the best form of his F1 career.

"I think I've never had a start of the season like this year, in terms of how competitive I felt in the car," Alonso said.

"I never started with a difference with my team-mate as this year, ever, and it's a team-mate that won in all the other categories, when they have equal cars, until Formula 1, so I have a very good reference."

Alonso said his personal performance is offsetting the frustration of McLaren's current struggles.

"I'm definitely at probably my best, so that's OK in terms of keeping motivation and keeping hunger for success, despite the results - because you know and you feel that you are in a very good moment of your driving career," he said.

Asked why he felt as strong as ever despite his F1 career now likely approaching its twilight, Alonso said: "You know and you learn many things in your career.

"If I raced against myself [from] 10 years ago, 15 years ago, I would be as quick as now probably.

"But you will make little mistakes here and there, you will overdrive sometimes.

"Now you will know when is time to push, when is time to be a little more conservative, you know how precise you need to be on the pitstop, fuel-saving techniques, starts, quali preparation, tyre preparation."