Bernard Bookey was sitting in front of his computer in his home in Radlett when he received his “warning”.

Bernard says his right eye “clouded over” and he lost all vision in it.

“I was sitting by my computer,” the 82-year-old recalls, “I was minding my own business and I just lost the vision in my right eye.

“I had enough time to get worried and then it began to clear.

“But it worried me enough to make me phone my optician and she said to me immediately: 'T.I.A'.”

The optician told Bernard he had experienced a transient ischaemic attack (T.I.A). He had had what is more commonly known as a “mini-stroke”.

It was a warning of a potential stroke Bernard was likely to have suffered had he not gone to hospital straight away and been treated by experts.

Dr Davis Collas, a stroke physician at Watford General said: “A number of people who might go on to get a stroke can get a warning first.”

He says mini-strokes can be anything from droopiness in the victim's face, to numbness down one side of the body, to a floppy arm.

“It can be very brief, perhaps between a minute and five minutes,” he said.

“It is really important those people get the right sort of assessment and treatment and that way we can reduce the chance of those people having a stroke.”

Approximately 125,000 people suffer a major stroke in the UK every year. Around a quarter of those people will have previously experienced a mini-stroke.

A recent television campaign to promote the warning signs of a stroke has seen an increase in the number of people contacting Watford's stroke prevention unit.

The unit was set up in South Oxhey in 1999. Now, at Watford General, it is a “one-stop shop” for stroke patients and has about 450 people referred to it every year. Of those, between 50 and 100 require surgery to clear an artery carrying blood to the brain.

“The treatment is very quick these days,” says Mr Sanjeev Sarin, a surgeon at the Vicarage Road hospital.

He says patients requiring surgery used to go under the knife within six weeks of having a mini-stroke. Now, they are seen between a week and a fortnight after diagnosis and patients don't even require a general anaesthetic.

He says: “It is not actually a very big procedure but it is very big in terms of the benefit it gives you.

“And if you are awake then you know the brain is working.”

Mr Sarin added: “Most strokes will have a warning, so as soon as someone has a warning we want them in hospital and to get them into the system – and we have a good system in place.”

Bernard, who was told last week he will not require surgery, says he is thankful he went for a check-up.

“I think I have been warned,” he says.

“But I think it is my nature to think the medical profession helps rather than hinders.”

He added: “I have even managed to loose 3lbs since last week – not by worrying though, by dieting.”