Special Olympics are vital - Stevie Wonder

Ambassador Stevie Wonder explains why he is involved with the Special Olympics which begin with the opening ceremony in Athens on Saturday.

The 13th World Summer Games run until 4 July and include 22 Sports across 30 venues in and around the Greek capital.

More than 7,000 competitors take part in the Special Olympics, one of the biggest sporting events of 2011 for people with learning disabilities.