Between 1942 and 1944 a very small, very secret, very successful clandestine unit of the Royal Navy, operated between Dartmouth in Devon, and the Brittany Coast in France. It was a crossing of about 100 miles, every yard of it dangerous. The unit was called the 15th Motor Gunboat Flotilla: crewed by 125 officers and men, it became the most highly decorated Royal Naval unit of the Second World War.
The 15th MGBF was an extraordinary group of men thrown together in the most secret of adventures. Very few were regular Royal Naval officers: instead the unit was made up of mostly Royal Naval Volunteer Officers and ''duration only'' sailors. Their home was a converted paddle steamer and luxury yacht, but their work could not have been more serious.

Their mission was to ferry agents of SIS and SOE to pinpoint landing sites on the Brittany coast in Occupied France. Once they had landed their agents, together with stores for the Resistance, they picked up evaders, escaped POWs who had had the good fortune to be collected by escape lines run by M19, as well as returning SIS and SOE agents.

It is a story that is inextricably entwined with that of the many agents they were responsible for - Pierre Hentic, Yves Le Tac, Virginia Hall, Albert Hué, Jeannie Rousseau, Suzanne Warengham, François Mitterrand and Mathilde Carré, as well as many others. Without the Flotilla, such intelligence gathering networks as Jade Fitzroy and Alliance would never have developed, and SOE''s VAR Line and MI9''s Shelburne Escape Line would never have been realised.

Drawing on a huge amount of research on both sides of the Channel, including private archives of many of the families involved, A Dangerous Enterprise brings the story of this most clandestine of operations brilliantly to life.