A 39-year-old Briton has been arrested on suspicion of using someone else's wireless Internet connection without permission, police said on Wednesday.
Officers spotted the man using a laptop as he sat on a wall outside a house in Chiswick, west London, on Tuesday.
He told officers he had browsed the Internet via an unsecured broadband link from a nearby house, Scotland Yard said.
He was arrested and later released on police bail to Nov. 11 pending further inquiries.
"This arrest should act as a warning to anyone who thinks it is acceptable to illegally use other people's broadband connections," said Detective Constable Mark Roberts, of the Metropolitan Police.
"Computer users need to be aware that this is unlawful and police will investigate any violation we become aware of."
The practice, known as piggybacking, breaches the Computer Misuse Act and the Communications Act, he added.
Earlier this year, a man and a woman were arrested in the Midlands for wireless theft as they sat in their cars.
Gregory Straszkiewicz, from west London, is believed to be the first person to be convicted of the offense in 2005. He was fined 500 pounds and given a 12-month conditional discharge.
Internet security experts say people should secure their wireless connections to prevent identity theft and fraud.