Imperial College Healthcare NHS Trust was formed on 1 October 2007 by the merger of Hammersmith Hospitals NHS Trust (Charing Cross Hospital, Hammersmith Hospital and Queen Charlotte's and Chelsea Hospital) and St Mary's NHS Trust (St. Mary's Hospital and Western Eye Hospital) with Imperial College London Faculty of Medicine. It is an academic health science centre and manages five hospitals: Charing Cross Hospital, Queen Charlotte's and Chelsea Hospital, Hammersmith Hospital, St Mary's Hospital, and Western Eye Hospital. The Trust is currently the largest in the UK and has an annual turnover of £800 million, treating more than a million patients a year.[citation needed]

What was formed on the 1st October 2007?