“We threw two rookies in with no pre-season testing and missing the first race altogether, and just to expect them to perform - which they have done - they’ve done an outstanding job,” team principal John Booth told Formula1.com.

Stevens started the year with just one Grand Prix start - Abu Dhabi 2014, with Caterham - to his name, while Merhi’s F1 outings had not extended beyond Friday practice runs - also with Caterham - last season. But despite their inexperience, Booth has been impressed.

“We’re over the moon with both drivers. Up until now we’ve given them a car that’s not been easy to drive and the engine must be at least 1-1.5 seconds slower than the best engine on the grid. We haven’t made their lives easy.”

At the start of the year it was Stevens who held the clear speed advantage, but in recent races the British driver has seen his Spanish team mate close the gap, and Booth believes the pair are now forming a solid - and mutually beneficial - relationship.

“They started getting very competitive a few races ago, but they seem to have had conversations themselves about how they want to conduct themselves on track,” he said. “They’re both very intelligent guys, and they know each other very well of course. I think they’re developing into a strong team now.”

As well as Stevens and Merhi, Marussia also have 2013 GP2 champion Fabio Leimer on their books as their official reserve, and Booth has not ruled out seeing more of the Swiss later in the year.

“Another excellent driver with a great pedigree,” he added. “We’ll do something with Fabio before the season is over for sure.”

Look out later this week for an exclusive and in-depth interview with Booth and Marussia president and sporting director Graeme Lowdon, discussing the team’s past, present and future.