People who drive are informed of the necessity to report the diagnosis to the DVLA and are provided with information on alternatives if they are advised to stop driving.

If you drive, you will need to make the DVLA aware of your dementia diagnosis. They will assess whether you can continue driving. (Those diagnosed with Mild Cognitive Impairment do not need to inform the DVLA.)
At some point you may no longer be able to drive. Your dementia advisor will be able to inform you about alternatives to driving.
 
For extra information, evidence and best practice please scroll down to the bottom of the page.

DVLA (2020) Assessing fitness to drive – a guide for medical professionals: "A person with dementia may be able to drive but must notify the DVLA. It is difficult to assess driving ability in people with dementia. The DVLA acknowledges that there are varied presentations and rates of progression, and the decision on licensing is usually based on medical reports. A formal driving assessment may be necessary."

Royal College of Psychiatrists, MSNAP standards for memory assessment: "People who drive are informed of the necessity to report the diagnosis to the DVLA (or equivalent vehicle licensing authority)."

British Geriatrics Society, Driving with dementia or Mild Cognitive Impairment Consensus Guidelines for Clinicians: The assessment of driving risk can be difficult for clinicians. These guidelines, endorsed by the BGS, set out the responsibilities of clinicians to their patients and provide a framework for thinking about the management of their driving safety. https://tfgm.com/drivesafe/safer-driving-for-longer-course AND GM Alternatives to driving leaflet Stockport