Meet the Jennings who are the first family in the world to be diagnosed with hereditary, early-onset Alzheimer’s - a discovery which many think will be the key to unlocking a cure at last.

Despite widespread belief that Alzheimer’s had no familial link, throughout the 1980s Carol Jennings lobbied doctors, urging them to explore a hunch that her father and his four siblings’ diagnoses were linked.

Years later, Carol’s fears were confirmed and a mutant gene for early-onset dementia was discovered within her family, which would ultimately shape their future.

This meant that Carol had a 50:50 chance of inheriting the condition, and if she did, her two children, John and Emily, would face the same risk. Carol chose not to test for the disease, but as she entered her 50s her health began to deteriorate.

The Jennings vs Alzheimer’s meets the Midlands family at a profound moment in the world’s understanding of the disease. After years of set-backs, two new drugs that slow the decline of Alzheimer’s are set to be licenced in the UK.

Emily and John now face an agonising choice about whether they should take the test to find out if they too carry the gene.

The Jennings vs Alzheimer’s, tonight at 9pm on BBC Two and iPlayer.