The cover is shot by Lord Snowden. (source)
UPDATED SEPTEMBER 04th 2011: Zara Phillips was photographed by Uli Weber for the cover.
30 year old Zara Phillips is the second child and only daughter of Princess Anne and her first husband Captain Mark Phillips and is thirteenth in the line of succession to the throne. She is married to England rugby union player Mike Tindall, but has elected to keep her maiden name for professional and sponsors, referring to herself otherwise as “Mrs Tindall”