The Spaniard posted a best time of 1m43.013s during the three-hour afternoon period of the FIA World Endurance Championship rookie test aboard the #8 Toyota TS050 Hybrid.

That compared with the 1m43.709s he set during the two-hour morning session.

Alonso's fastest lap of the day compared with the 1m42.381s set by Toyota regular Mike Conway aboard the #7 car in the afternoon.

The McLaren Formula 1 driver, who has targeted a Le Mans 24 Hours win as part of a bid to win the triple crown of motorsport, joined Conway in a Michelin tyre test during the afternoon.

Toyota Motorsport GmbH technical director Pascal Vasselon stressed that Alonso did not go for a quick time at any point.

"We did not do any low-fuel run and we did not do any qualifying runs — there was no trophy today to win," he said.

"We’ve done a bit more work with Fernando. After getting more familiar with the car this afternoon he did some tyre testing, complementing what Mike [Conway] has been doing in the other car."

Alonso called the test with Toyota as "a great day".

"I think a test in an LMP1 is always a nice thing for any racing driver; these cars are amazing to drive and are very consistent in the stints," he added.

He refused to be drawn on the likelihood of him joining Toyota for Le Mans next year.

"One day it would be nice [to race in endurance]," he said. "I don’t know when, but endurance for sure is one of the goals for me in the future after F1."

Vasselon refused on to comment on the chances of Alonso rejoining Toyota for its next scheduled test at Aragon at the start of next month.

"At the moment it was just a fantastic opportunity," he said. "We have time now to think about the future."

Fittipaldi ends up top rookie

Pietro Fittipaldi, who was given a test in a Porsche 919 Hybrid for winning the Formula V8 3.5 title over the Bahrain WEC weekend, also improved his time.

The grandson of Emerson Fittipaldi got down to a 1m42.275s during a short run in the afternoon, knocking more than a second off his morning best and ending the day as top rookie.

The fastest LMP2 time was again set by Formula V8 3.5 driver Konstantin Tereshchenko in the TDS team's Oreca-Gibson 07.

The Russian improved by nearly half a second on his morning best to get down to a 1m48.444s.

Nick Tandy and Earl Bamber tested for the factory Porsche GTE Pro squad in the afternoon the day after their final outings in an LMP1 car.

They look certain to rejoin Porsche's IMSA WeatherTech SportsCar Championship team in 2018.

Kevin Estre set the best time in class in the afternoon in the sister 911 RSR, a 1m57.663s.