A dramatic day for Mercedes on several levels

Mercedes have had quite a day' first they announce the exciting news that they are to add two big names from main rivals Red Bull to their ever-growing roster of technical staff by employing Mark Ellis and Giles Wood.

Then Nico Rosberg suffered a Pirelli tyre failure at 320km/h on the final day of the three day Bahrain test, ending Mercedes' activity at the test.

Rosberg was moved to Tweet about it: "Just spun at full speed 320km/h on Bahrain straight cause my tyre blew up without warning," he wrote. "Thanks to that need to get some toilet paper now"

However he was clearly asked to take the Tweet down soon afterwards. Nevertheless it had been screen-grabbed and is widely in circulation.

Pirelli issued a statement some hours later saying that the tyres being tested in Bahrain were "prototypes" and adding, "Nico Rosberg’s Mercedes was fitted with one of these prototypes, a tyre which had only been tested in the laboratory and which will not be proposed again.

Thus, the safety of the tyres which will be supplied for the next Championship is not in question."

The signing of Ellis and Wood, who are contracted to Red Bull until June 2014 adds to the list of significant engineering players to leave the Milton Keynes squad, following chief aerodynamicist Peter Prodromou, who has agreed to join McLaren in 2015.

Red Bull has dominated the sport since 2010, with design and aerodynamics being at the forefront of their success.

For Ellis, Red Bull’s head of vehicle dynamics, the move is a return to familiar ground after previously working as chief engineer for BAR Honda up to 2008 - having input on the 2009 Brawn. He returns to Brackley as Performance Director, working alongside Bob Bell, Geoff Willis, Aldo Costa. Paddy Lowe takes over one half of the team; the technical and racing side of the operation with the departure of Ross Brawn.

Wood, meanwhile, has been chief engineer of simulation and analysis since a switch from McLaren in 2010, and he takes up the role of chief engineer for simulation and development.

The appointments are the first under the new leadership of Lowe and Toto Wolff, who have a difficult task ahead of them. Lowe's commitments as Executive Director will require him to fill the boots of Ross Brawn and the responsibilities that come with that.