The first European round of the 2015 Formula 1 World Championship season is set to see several teams bring their first significant wave of upgrades this year, though it is the gains proposed by McLaren that is set to attract more attention than most.

Following a floundering start to its rekindled relationship with Honda, McLaren has shown glimmers of promise in the most recent races in terms of performance, even if persistent gremlins experienced by the non-starting Jenson Button in Bahrain suggests reliability remains a big concern.

Even so, with Eric Boullier suggesting in February that it will take until Spanish Grand Prix before McLaren can consider itself as competitive, many are holding him to his word with all eyes on whether the MP4-30 can firm its burgeoning mid-field status - or better - and challenge for its first points of the season in Barcelona.

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Indeed, though Boullier and Fernando Alonso have sought to play down the significance of the Barcelona upgrades, the McLaren racing director confirms it will see the biggest overhaul on the car since the start of the year.

"McLaren and Honda are really operating like one team, which is good. A lot of progress is being done on mapping because these engines, obviously, have a lot of internal performance in mapping and fuel efficiency, power, driveability, energy deployment - there are many, many mappings now and this part of the McLaren-Honda team is now operating at a good level, still not like we want but at a good level now.

"So we can extract quicker some performance and, from Barcelona, we should have some new technologies in the engine which will allow us to get more performance out of the car."

The McLaren-Honda has been praised for its handling ability and the confidence it gives the drivers, though the Honda power unit - which is still striving for durability - has suffered in the speed traps.

Nonetheless, qualifying for the Bahrain Grand Prix was notable for Alonso's McLaren proving quicker though the speed traps than three of the Renault-powered cars, albeit still 15kph down on the top pace set by Felipe Massa's Mercedes-powered Williams