New look of Silverstone Formula 1 track

The historic Silverstone circuit, home to Formula 1 British Grand Prix, has been modified once again.

Although some of the bigger changes were made before the last race in July 2010, this year drivers and spectators will see a new pit lane and different positions for start and finish lines.

Drew MacDonald of Populous, the company that designed the track, explains the changes - and tells the BBC why circuit design is extremely important in racing.