McLaren has fired up its new Mercedes Formula One engine for the first time.
McLaren and Mercedes have rekindled their former partnership for 2021 and beyond. McLaren ran Renault engines from 2018 until last year.
New signing Daniel Ricciardo will join Lando Norris in spearheading McLaren's new era as it looks to continue the upwards trajectory of recent seasons.
On Wednesday, the British team fired up the engine for the first time, something which is a key part of the build of a new car.
McLaren CEO Zak Brown and team boss Andreas Seidl were on hand to overseen the engine fire-up, which did not reveal anything of the team's new car design or livery.
The McLaren-Mercedes partnership was supposed to take place at the same time as a major revamp of the sport's aerodynamic rules. That rule change has been pushed back to 2022 to save on development costs during the coronavirus pandemic.
While most other teams will have the majority of its car unchanged this season, McLaren was forced to spend its developmental tokens last year on fitting a brand new engine rather than on 2020 upgrades.
McLaren effectively has a new car this year as a result.
"Whereas every other team will carry over most of its car from last year into this year, our switch to the Mercedes power unit means that's not the case for us," said McLaren production director Piers Thynne is quoted as saying by Autosport.
"It's driven a huge amount of change and, essentially, we've been building a new car. The number of new parts on the MCL35M is about the same as when we built the MCL35.
"The back of the chassis and gearbox bell housing around the engine have changed significantly to adapt to the new power unit.
"Changing power unit greatly alters the architecture of the car and the way everything is packaged, so the entire cooling layout and all the pipework, be that for fluid or air, has changed, along with all electrical harnessing and control boxes.
"There are some significant elements of carryover as we enter the cost cap.
"The FIA created a list of Transitional Carry Over (TCO) components that are outside of this year's cost cap. These are parts that can be used in 2021 if they were run on last year's car.
"We've pushed these TCO regulations to the absolute maximum to allow us to carry over as much as possible, such as gearbox internals and some suspension components, and therefore not have to use a portion of our 2021 budget on their design and production."
Pre-season testing will take place in Bahrain between March 12-14. The Bahrain Grand Prix will start the season on March 28.