Head: I regret Ralf leaving

Schumacher has been with the team since 1999, marking the longest period any driver has spent with the Grove-based team. But the German will now head to pastures new at Toyota.

"I do really regret Ralf leaving us," said Head told the Williams website. "But after six years, it was the right time for both parties to look for new solutions. We really wanted to win the World Championship these six years, but unfortunately we didn't succeed in achieving this goal."

Schumacher contested a total of 95 grands prix with the team and taken six victories. He took his first win as under the BMW and Williams partnership in 2001 at the San Marino Grand Prix and celebrated his last victory for the team in 2003 at Magny-Cours.

Schumacher himself looks back extremely fondly at the past six years. "It has been a long but beautiful time," he said. "It is anything but easy to leave the team after six years."

Former team-mate Juan Pablo Montoya is also leaving the team at the end of the year to take up his seat at McLaren. Australian Mark Webber has already signed for the team while his partner next year has yet to be announced.

Test driver Antonio Pizzonia is believed to be team boss Frank Williams' favourite, but the team is also testing BAR test driver Anthony Davidson and Jordan's Nick Heidfeld.