The Duchess of Cornwall saw first-hand how medical alert dogs assist their owners during a charity visit on Wednesday.

Camilla was opening the new Medical Detection Dogs (MDD) 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 postural orthostatic tachycardia syndrome (POTS), and has had Henry for almost a year.

She said: “When I’m standing up or upright, my heart rate rapidly increases and my blood pressure drops which causes me 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.

Royal visit to Milton Keynes
The Duchess of Cornwall pets a friendly dog during her visit to the new centre (Eddie Keogh/PA)

She explained: “Henry will alert to my black-out, but also extreme palpitations and dizziness.

“He can let me know about five minutes before. He’ll jump up at me, and if I’m really not paying attention he will bark at me.”

Miss Draper paid tribute to the charity, which is helping her to complete her education, saying: “I don’t know where I would be without Medical Detection Dogs, I highly doubt I would be in university without them.”

Royal visit to Milton Keynes
A dog guard of honour was held for the Duchess (Aaron Chown/PA)

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 wide variety of the charity’s facilities, including puppy training and a veterinary room, and eight of their dogs performed a guard of honour as she cut the ribbon to officially open the new centre.

Royal visit to Milton Keynes
Camilla has been a patron of the charity since 2014 (Eddie Keogh/PA)

Not all of the canines were on their best behaviour, however, as charity mascot Ember, a Golden Retriever Labrador cross, attempted to get her nose up Camilla’s skirt.

Camilla has been a patron of the charity since 2014, and co-founder Dr Guest thanked her for her support, and said: “I can’t say enough how things have changed.

“I was the mad dog lady, now I’m a scientist.”