But it was Ferrari who sizzled in pre-season testing to emerge as the early favourites in Australia, with Hamilton claiming the Italian team could be up to half a second quicker around Albert Park on Sunday.
Hamilton will be looking to draw first blood in his battle against the Ferraris of Vettel and Leclerc in Australia, but could his Mercedes teammate Valtteri Bottas emerge from a torrid - and winless - 2018 and put the pressure on the reigning champion?
The German had appeared firmly in the title fight but his season seemed to take a downturn after failing to win the German Grand Prix, crashing out at the end having led the race.
"We never sit still so we've got to evolve our track", Westacott said.
Mercedes AMG F1 2019 Barcelona Pre Season Test 2 Day 4 – Steve Etherington
Max Verstappen, who at 17 was the youngest driver ever to start a race, is now a 21-year-old "veteran" in his fifth season and the main man at Red Bull, who also have 23-year-old Frenchman Pierre Gasly racing for them. Sebastian Vettel and Charles Leclerc will drive for Ferrari this year.
CHiQ TVs in play at last year's Grand Prix event. "So far the atmosphere is good, the spirit is right within the team and we will try to carry that into the season".
"But an F1 season is not just about who comes out of the blocks quickest", he added. 'So far, the spirit is right, the team is on track, the vehicle feels good so let's see how we start the year.' Hamilton, meanwhile, is braced for a scrap.
But Hamilton swatted aside suggestions that Mercedes is trying to play down its expectations.
Mercedes have done that in the past, but there is a growing feeling in the paddock that Ferrari could have the edge this season, with a new team principal in place, after Mattia Binotto replaced Maurizio Arrivabene, and a faster vehicle. The 29-year-old Finn is now entering his third year with the world champions and says it is time to be more selfish in order to achieve his career goal of winning the world championship. "It is the second debut for me after being away from the sport for many years".
Dick Cheney Compares Trump's Foreign Policy to Obama's
In a private session, the former vice president told the current one that Trump's policy looks too much like Barack Obama's. The debate took place during Cheney's interview of Pence for those in attendance.