All four of the experienced single-seater racers ran in the season-two Mahindra test car in Spain last month.

One of them is expected to join Bruno Senna in the Campos Racing-run squad for the second season of the all-electric series, which begins in Beijing on October 17.

A Motorsport.com source who attended the test stated that Adam Carroll emerged the quickest by just over 0.3s from Felix da Costa, while Carroll’s former GP2 team mate Pantano was a further 0.3s behind.

“It was interesting to see how the drivers adapted, as they all have good pedigrees in Formula racing but only one had experience in a Formula E car,” said the source, who wished not to be named.

“They all did a very good job as you would expect, but Carroll really impressed everyone with his instant speed and feedback.”

Motorsport.com can also reveal that Carroll was also invited to test for reigning champions NEXTEV TCR. The run, which also took place last month, saw the Northern Irish racer drive the Campos-run NEXTEV TCR Formula E 001 test car.

The multiple GP2 race winner and A1 GP champion is believed to have impressed in that test as well.

Oliver Turvey is expected to join Piquet in a full-time role in the team for season two after his assured performance at Battersea Park in June. The factory McLaren driver is, however, set to miss the first Donington test day next week, as he will be racing in the Super GT championship at Fuji.

Carroll is no stranger to the Campos team, having won an Auto GP race for the team in 2011. The 32-year-old is highly-rated by many single-seater observers and is often ranked as one of the best drivers never to have started a Grand Prix, although he was a test driver for BAR Honda in 2005.

Should Buenos Aires ePrix winner Felix da Costa be chosen for the seat, the Portuguese would miss at least two events of the 2015-16 season, including the opener at Beijing due to his DTM commitments with BMW.

Pantano, 36, contested the 2004 Formula 1 season with Jordan and was the 2008 GP2 champion, but has not driven a single-seater competitively since a one-off appearance for the Chip Ganassi IndyCar team at Mid-Ohio in 2012.

Mahindra is expected to announce its drivers at Donington Park next Monday.