â€˜Would you like to see my art?â€™ Stephen Wiltshire looks me steadily in the eye then leads the way around his gallery in Pall Mall, London, stopping to explain each and every picture.
Many are cityscapes: panoramas of London, Rome, New York, Paris, Tokyo and Hong Kong. All are detailed, ambient, filled with character.
Landmarks such as Big Ben and Buckingham Palace are rendered with draughtsman-like ease. Street scenes in pen and ink â€“ peak hour Piccadilly, downtown Manhattan â€“ are enlivened with the use of a single colour.
â€˜Red buses are my favourite,â€™ says Wiltshire. â€˜Red buses and yellow taxis.â€™
There are prints, postcards and books for sale. The 2010 Stephen Wiltshire calendar, like his 1991 book Floating Cities (number one on the Sunday Times bestseller list for weeks) is sold out. An original drawing of the Sydney Opera House is for sale at Â£10,500 ($17,370), payable in easy interest â€“ free instalments.
Unlike most of Wiltshireâ€™s sketches, which he begins after visiting a city (often flying over it in a helicopter) the Opera House image was created after a glimpse at a photograph.
When Wiltshire arrives in Australia for the first time next week, heâ€™ll create an image of Sydney from memory, after he has observed the city from either the top of Sydney Tower or the Harbour Bridge.
People are invited to Customs House at Circular Quay to watch him work.
â€˜I like it when people come to see me drawing,â€™ says Wiltshire, whose displays of talent have been filmed by the likes of US television network CBS, Britainâ€™s BBC and 2007, Australian 60 minutes.
â€˜It makes me feel happy and it makes a lot of people smile,â€™ he adds, smiling himself. â€˜They say how good my work is. Some people call me a genius. I feel very proud.â€™
Wiltshire, 36, commutes to the gallery from the home he shares with his mother in Maida Vale, West London. Today the ground floor of this cosy 19th-century shop teems with visitors. A family â€“ dad, mum, brother, sister â€“ stands before a drawing of New Yorkâ€™s iconic skyline, emitting the occasional â€˜wowâ€™.
This work, a commission, was created after Wiltshire spent just 20 minutes in a helicopter, gazing at the skyscraper-filled panorama. He then spent a week working in short sharp bursts: sketching the layout in pencil, scaling it within the border, adding in landmarks and filling in the detail.
His powers of recall have dumbfounded art lovers and doctors alike. The Colosseum in his panorama of Rome is virtually a blueprint. His Pantheon has the exact number of columns.
That Wiltshire happens to be autistic makes his virtuosity all the more astounding.
One of two children born in England to West Indian parents â€“ his mother was a seamstress; his father an electrical engineer who died in a motorbike accident when Stephen was three â€“ he was a withdrawn, almost totally mute child who avoided eye contact and interaction with others and endured debilitating nervous tic.
Art was his only distraction. He would rush into other rooms to stare intently at pictures and loved to scribble away, totally absorbed, for hours.
Teachers at his special needs primary school encouraged him to form words by temporarily removing his art supplies. â€˜Pencil,â€™ he said one day, though he wouldnâ€™t speak fully until the age of nine. â€˜Paper.â€™
A section of the gallery is dedicated to his early work; his slightly wonky Albert Hall is the first drawing in his prize-winning 1984 London Alphabet series (the last was London's zoo).â€™
Thereâ€™s a sketch of his older sister Annette, who helped him launch the Stephen Wiltshire Gallery in 2006, and who will be accompanying him to Sydney.
Thereâ€™s also a portrait (â€˜In pencil, from memoryâ€™) of New York-based British neurologist and author, Oliver Sacks.
It is (Wiltshireâ€™s) genius which sets him apart and confers on him the status of an artist,â€™ Sacks wrote in his foreward to Floating Cities. â€˜For a child who was once locked within the prison house of his own private world this thrilling development of language, laughter and art is nothing short of a miracle.â€™
â€˜Hi, Iâ€™m Stephen,â€™ says Wilshire, introducing himself to the family in front of the New York panorama, repeating each of their names in turn and accepting their praise with practised grace.
We move on with our mini-tour, past his famous drawing of Londonâ€™s St Pancras station, which he completed while taking part in a 1987 BBC program about savants with extraordinary talents, The Foolish Wise Ones.
The BBC was inundated with calls and letters from viewers eager to buy his artwork (he was labelled â€˜the best child artist in Britainâ€™ by Hugh Casson, former president of the Royal Academy of Arts).
His commissions have increased steadily since his gallery opened.
The public exposure from The Foolish Wise Ones won him a mentor in the form of literary agent Margaret Hewson, who arranged his first visit to New York, oversaw his book deals, established a trust in his name and helped him enrol in a three-year degree at City and Guilds of London Art School.
Today heâ€™s a role model and inspiration for young people everywhere. Twice featured in the list of the 100 most influential black people in Britain, and awarded an MBE for services to the art world in 2006 (no specific mention of his disability was made in the citation). Wiltshire is living testament to what can be achieved when potential is realised and developed early on. Just donâ€™t call him the Human Camera. His family donâ€™t like it and anyway, his work is too soulful, too moody, to be reduced like that.
A sketch of American classic cars â€“ Oldsmobile, Pontiacs, Chevrolets (â€˜I collect all the models; I love the metallic colours the bestâ€™) - cleverly evokes another era. An early portrait of a white-suited John Travolta on the dancefloor â€“ one arm pointing skywards â€“ captures all the boundary-breaking possibility, all the triumph over adversity of Saturday Night Fever (Wiltshireâ€™s second favourite movie after Rain Man).
I tell him that the Bee Gees (who did the soundtrack) grew up in Australia and he nods happily. â€˜I love disco musicâ€™ he says.
Disco, pop, funk and R&B all jostle for prominence on Wilshireâ€™s iPod, his essential accessory whether working in public or in his tiny studio atop and narrow spiral staircase on the galleryâ€™s first floor.
Music helps him concentrate and focus, partly because he is musically inclined himself. â€˜I have been playing piano for over 15 years with my piano teacher Evie,â€™ he says.
â€˜I am really good at playing Stand By Me by Ben E. King and Wonderful World by Sam Cooke on the piano. I also sang My Cherie Amour by Stevie Wonder at my sisterâ€™s wedding.â€™
For someone who couldnâ€™t cross the road by himself until he was a teenager, Wilshire has exceeded expectations, and developed to an extent that no one thought possible.
After I leave him talking confidently to a new set of visitors, I stop at the door and glance back at this remarkable, engaging man. He catches my eye then gives me a wave and a smile.