The Duchess of Cornwall saw first-hand how medical alert dogs assist their owners during a charity visit.
Camilla was opening the new Medical Detection Dogs training centre near Milton Keynes when Henry, a three-year-old Golden Retriever, jumped up to alert his owner to her increased heart rate.
Elizabeth Draper, 23, suffers from a heart condition which can cause her to black out. Having been trained with sweat and breath samples from Miss Draper, Henry can detect changes in her body and lets her know she could be about to fall unconscious.
Miss Draper paid tribute to the charity, which is helping her to complete her education.
MDD was founded in 2008 by Dr Claire Guest and Dr John Church, who believed that dogs' powerful noses could help detect disease.
They now train medical alert dogs to work alongside people with health problems such as diabetes and nut allergies, as well as other specialist dogs who can detect diseases such as cancer and Parkinson's.
The Duchess saw a variety of the charity's facilities, including puppy training and a veterinary room. Eight dogs performed a guard of honour as she cut the ribbon to officially open the new centre.
Camilla has been a patron of the charity since 2014, and co-founder Dr Guest thanked her for her support