Bruce Willis' first frontotemporal dementia (FTD) symptom was the return of his stutter

She told Town and Country magazine: "For Bruce, it started with language. He had a severe stutter as a child.

"He went to college, and there was a theatre teacher who said, 'I've got something that's going to help you.' From that class, Bruce realised that he could memorise a script and be able to say it without stuttering. That's what propelled him into acting.

"Bruce has always had a stutter, but he has been good at covering it up. As his language started changing, it [seemed like it] was just a part of a stutter, it was just Bruce.

"Never in a million years would I think it would be a form of dementia for someone so young."

The 46-year-old model - who has daughters Mabel, 12, and 10-year-old Evelyn with the 69-year-old star - is planning to write a book about her family's experiences in order to "take some control back" and to celebrate the positives in their story.

She said: "We had so many plans, so many beautiful things we wanted to do with our girls, so many things that we wanted to experience together. You just rip that page out completely, and then how do you rewrite the story?

"I'm learning how to take some control back. It might not be the most beautiful story I could have thought of, but there are cracks of light.

"There's been an enormous amount of strength and a lot of beautiful things that have come from this diagnosis, and I'm trying to throw it back into the pot so other people can know that they will be okay over time."

And Emma hopes her book will be able to help others in a similar position.

She said: "It's not just about how to care for your loved one, it's about how to look after yourself in the process.

"All these experts and clinicians who have helped me find my own footing in this have said, 'You cannot be a caring partner for your loved one if you are not caring for yourself.'

"This book is about all the emotions that come with caregiving: the sadness, the grief, how traumatic it is, but also resentment and anger, and all these emotions that you're not allowed to talk about. It's the book that I wish I had been handed when we got the FTD diagnosis.

"I wish I had heard from someone, like, "I know this feels horrible and very traumatic, but you're going to be okay."