'Memory' artist Stephen Wiltshire exhibits in New York
Helped by his autism, Stephen Wiltshire started to draw before he could talk.
Today he has his own gallery in Pall Mall, central London, and produces intricate pen and ink studies entirely from memory.
Mr Wiltshire's most high profile commission was in New York, when he took a helicopter ride and reproduced the city skyline in just four days.
He has been explaining how a 75m (245ft) long version of his drawing is to go on show at New York's JFK airport.