Harvey Nichols is a British Department store chain founded in 1831. It’s Flagship store is in Knightsbridge, London.
The dress must have been either custom made for the deb or must be a special edition piece.
Harveynichols.com, (2015) Store Details – Knightsbridge – Designer Fashion, Beauty, Food & Wine – Harvey Nichols. Available at: http://www.harveynichols.com/store/knightsbridge/ (Accessed: 2 December 2015).