This day was established in 2010 to provide a focal point for raising awareness about the many people in the UK and around the world who continue to be trapped in modern slavery, and to promote the need for many individuals and organisations across society to play a part in ending it.
A parliamentary bill to create the day was championed by former MP and now Chairman of the Human Trafficking Foundation, Anthony Steen. The date also coincides with the European Anti-Trafficking Day.
http://www.antislavery.org/english/antislavery_day/