You are stuck in a busy, noisy, unfamiliar building. You are unsure of where you are or even what time of year it is. All the corridors look the same. You find it hard to judge how far away the floor is. You can't remember where the toilets are. You can't remember why you're here. You feel a rising sense of panic as you search for clues to where you are, and even who you are.
Perhaps the cruelest aspect of Alzheimer's is that it robs families of their loved ones before they are truly gone. Loss of memories and physical abilities frustrates patients and pains family. Every health professional who works with Alzheimer's looks forward to the day when patients can be told there is a cure.
The new figures show more than twice as many people in the UK have dementia before the age of 65 than was thought. It's estimated 42,000 people have young onset dementia (also called early onset dementia) - including thousands of cases among those in their 40s, and more than 700 cases among those in their 30s.
I am always immensely uncomfortable when anyone tries to put a monetary value on dementia, purely because I know that there is so much more to calculating the 'cost' of dementia than could ever be accurately represented by the use of pound signs. The emotional, all-encompassing, life-changing (and life-shortening) effects of dementia reach far and wide into every family affected.
I had one last thing to do in London before going home to my parents in Hampshire, and that one thing is to visit my mother-in-law. My MiL is in the grips of Alzheimer's disease. She does not recognise me. She lives in a world where her parents are still very much alive, where she still goes to work. I no longer exist in her world.