A stray sandwich wrap that became lodged in the brake ducts of Fernando Alonso’s Alpine car caused his retirement on his race return to Formula 1 at the Bahrain Grand Prix.

The two-time world champion’s first F1 race since the 2018 Abu Dhabi Grand Prix came to a premature end after just 33 laps when he was forced to pit with overheating brakes after debris got stuck in his car.

Alpine called Alonso in to the garage when the team noticed his brake temperatures had sky-rocketed, with executive director Marcin Budkowski revealing the bizarre cause of his retirement after the race.

“After his first stop we had a small issue that forced us to reduce the performance of the car, then after the second stop, a sandwich wrap paper got stuck inside the rear brake duct of Fernando's car, which led to high temperatures and caused some damage to the brake system, so we retired him for safety reasons,” he explained.

"It was a very unlucky first race for Fernando considering how strong he looked.”

After qualifying ninth, Alonso had looked in contention to record a points finish on his F1 comeback until he experienced problems with energy deployment in his power unit and began slipping down the order.

The 39-year-old Spaniard admitted his return to F1 was emotional, despite being short-lived.

“It was a shame that we could not see the chequered flag today because I really enjoyed the whole thing,” Alonso said.

“It was nice to be back racing. It was nice to feel again the adrenaline at the starting grid, the national anthem, all these procedures were very emotional today for me.

“The race itself was fun at the beginning with the start, couple of good battles on the track in the first stint and then unfortunately we had to retire the car with a brake issue that is still under investigation, but apparently there is some debris on the rear brake duct.

“Nothing we can do now. More just thinking to Imola and hopefully get some points there.”