“My yesterdays have disappeared, my tomorrows are uncertain, but I have today.” So says Alice, a Harvard professor diagnosed aged 50 with early onset dementia as she gives a lecture on what it is like when the person you once were is fading away and you know it is happening.“I miss my used-to-be self”, she says. This is the third play about Alzheimer’s at Cambridge Arts Theatre and the second this year but by far the most moving.

“My yesterdays have disappeared, my tomorrows are uncertain, but I have today.” So says Alice, a Harvard professor diagnosed aged 50 with early onset dementia as she gives a lecture on what it is like to be her.

“I miss my used-to-be self”, she says.

This is the third play about Alzheimer’s at Cambridge Arts Theatre and the second this year but by far the most moving. Sharon Small is luminescent as Alice, you understand her changing world and feel for her. I’m guessing that very few people in the audience weren’t thinking, that could have been me.

There is fine support too from Eva Pope as “Herself” the aware Alice who answers Alice’s alarmed questions - until there is no more Herself and she has stopped recognising her husband and children.

They are convincing as two parts of the same person and complement each other wonderfully.

The play, like the film, has been inspired by Lisa Genova’s novel, all three called Still Alice.

Such is the desperation about this condition that Genova’s Ted Talk, What You Can Do to Prevent Alzheimer’s has been viewed over two million times in its first few months online.

But the pertience of the subject matter apart, this is a fine piece of drama. It has been delicately adapted by Christine Mary Dunford, intriguingly designed by Jonathan Fensom and crisply directed by David Grindley.

This is an ensemble piece with strong, natural and adroit performances from the entire cast: Martin Marquez, as Alice’s husband, John, Ruth Olman as daughter Lydia, Mark Armstrong as son Thomas, Micah Balfour as Dr Davis and Anna Andresen as Dr Tamara and other roles. They are all exemplary in their portrayals of human beings caught up in a rolling condition, that apparently we can no more stop than the waves of the sea.

I entered the theatre asking myself if we needed yet another play about dementia and I expected it to be dreary. It isn’t. It’s electric. Superb performances make it fast-paced and engaging from start to finish.

Still Alice is at Cambridge Arts Theatre until Saturday, October 20.