The 71-year-old journalist, who has appeared on TV screens for nearly five decades, said he began to feel "discombobulated" around "six to nine months ago," and so went to see his doctor.

Stewart said: "I wasn't becoming forgetful but things like doing your shoelaces properly… making sure your tie was straight, remembering that the call time for your programme is four o'clock and not five o'clock, not turning up early or late, and stuff like that."

He also said his "very short-term memory is tricky" and "motor skills [are] very tricky".

Stewart told GB News that scans revealed he had had a series of minor strokes which led to a diagnosis of vascular dementia.

Dementia is caused by reduced blood flow to the brain and has symptoms including slowness of thought and problems with concentration.

One in 11 people in the UK aged over 65 have dementia, according to the NHS.

The veteran broadcaster said he has stopped smoking, is taking long walks with his dogs and completing word puzzles all in a bid to improve his physical and mental health.

Stewart said the thing he had found "most difficult to deal with" was the impact on his wife of 43 years, Sally, saying she had been reduced "almost to a carer".

He said she had to make sure he was ready before appearing for the interview and that his "tie was done properly".

Alzheimer's Research UK executive director Samantha Benham-Hermetz said: "Our thoughts are with Alastair Stewart and his family, following the news he has vascular dementia. We applaud Alastair's brave decision to share his diagnosis publicly and raise awareness, while also urging others to seek help if they have their own concerns about dementia.

"By speaking so openly and honestly about his experience, we hope this will put a further spotlight on the desperate need to find new treatments for all forms of dementia."

Despite being the second most common form of dementia, behind Alzheimer's disease, there are currently no treatments for the syndrome, which affects around 180,000 in the UK.

Stewart, who spent more than 35 years with ITN, joined GB News in 2020, but announced his retirement in March.

Stewart and his wife have four children together and live in Hampshire.