An 80-year-old British man diagnosed with dementia three years ago has been offered a record deal after online videos of him singing in the car went viral.

Ted McDermott, known as Teddy Mac, has been signed up by Decca Records after 'car karaoke' videos posted by his son Simon were watched 40 million times online.

Simon found that singing as the two drove round Blackburn, in northern England, helped his father cope with his Alzheimer's disease.

He posted videos of the drives with his father online to increase awareness for the Alzheimer's Society, after the advice and support the McDermott family received from the organisation's national Dementia Helpline following their father's diagnosis.

More than $197,000 has been raised so far.

"This is a dream come true not only for Dad but for the entire family," Simon McDermott told the Alzheimer's Society.

"There have been some really tough days in the last few years, especially for Mum. The more the Alzheimer's kicked in, the more Dad became aggressive, both physically and verbally.

"It was incredibly difficult to manage and terrifying at times."

Teddy Mac has signed a record deal after decades working as a holiday camp entertainer. ( Facebook: The Songaminute Man )

Mr McDermott has difficulty recognising his son but after decades working as a holiday camp entertainer could remember the words to a number of Frank Sinatra songs, including Quando, Quando, Quando.

Jeremy Hughes, chief executive at the Alzheimer's Society, said music could have a positive impact on people with dementia and that favourite songs or pieces could also be powerful prompts for reminiscence.

"This is clearly the case when Teddy sings and is transported back to his time as an entertainer," Mr Hughes said.

Now Teddy Mac will be headed for chart success with his own version of the Frank Sinatra classic You Make Me Feel So Young, to be released September 23.

Royalties from the single will be split between the Alzheimer's Society and the McDermott family.