Intro:

The Williams Formula One team lunch 2015 challenger - the FW37 - as first pre-season test gets underway at Jerez, Spain on Sunday (February 1).

Mercedes officially launch their 2015 Formula One car at the Jerez circuit in southern Spain on Sunday (February 1).

Script:

The Williams Formula One team unveiled their 2015 machine shortly before the first official pre-season test got underway at Jerez on Sunday.

Drivers Felipe Massa and Valtteri Bottas unveiled the FW37 in the pit lane as dawn broke.

Williams enjoyed a resurgence in 2014 as it became a regular podium finisher on its way to finishing third in the constructors' championship under the guidance of renowned team boss Frank Williams.

Valtteri Bottas is scheduled to take driving duties on the first day of testing in Spain on Sunday.

Meanwhile, defending world champions Mercedes also left it late, but finally took the wraps off their 2015 F1 challenger - the W06.

Lewis Hamilton scooped the drivers crown last season and the German manufacturer took the constructors' title over a dominant 2014.

With few rule changes for the new season more of the same is expected from Hamilton and team mate Nico Rosberg when racing gets underway in Australia for round one.

The seventh 'Silver Arrow' to compete in the Formula One World Championship takes to the track on Sunday,

Rosberg, last season's championship runner-up, will be behind the wheel for the first day of the three day pre-season test.