Seeing Is Not Always Believing...

Following his wife's death six years ago, David Stannard has become accustomed to spending quiet evenings alone at his home in Walton-on-Thames, Surrey.

So it came as a surprise to the 73-year-old when he looked up from his television one evening to discover he was sharing his living room with two RAF pilots and a schoolboy.

Mr Stannard's guests never said a word and vanished after 15 minutes. That night, he says, the walls of his house, which had always been white, looked as though they had been redecorated in patterned wallpaper with a brickwork effect.

It would be easy to dismiss Mr Stannard's story as the bizarre imaginings of an elderly mind. Fortunately, he knew he wasn't losing his mind; neither was his house haunted.

A few weeks earlier he had been registered blind, though he was still able to watch television if he sat at a certain angle. He'd been warned that as his eyesight deteriorated, he might experience visual hallucinations in the form of Charles Bonnet Syndrome (CBS).

An estimated 100,000 people in the UK have CBS, but many won't realise it because the condition remains something of a mystery.

The real number is probably higher because sufferers are often too ashamed to talk about what they have seen for fear of being considered crazy.

The condition was named after Charles Bonnet, an 18th-century Swiss natural philosopher whose grandfather had seen people, patterns and vehicles that were not really there. Bonnet was the first person to identify that you could have visual hallucinations and still be mentally sound.