A man has admitted making 15,000 explicit phone calls to women for his sexual gratification.
Paul Kavanagh, 41, picked his victims at random, claiming he was a market researcher for Marks & Spencer.
The call would invariably end with Kavanagh detailing what he would like to do to them.
Kavanagh, of Westbourne Park Road, west London, pleaded guilty to one count of causing a public nuisance at Southwark Crown Court.
Some of his victims, who were called repeatedly, ended up too scared to answer any of their phones, the court heard.
Kavanagh, a market stall worker, used a pay-as-you-go mobile for most of the calls.
When a gym opened opposite his flat, he pestered the receptionists he could see from his bedroom with up to 16 phone calls a day.
Police were able to move in when he told one of the receptionists he liked the way her hair was looking that day, signifying he was able to see the gym reception from his flat.
Officers estimated Kavanagh, who was arrested in July, had made between 10,000 and 15,000 calls in just 20 months.
When interviewed, he admitted while they were for his own "sexual gratification", he was glad he had been caught so his "addiction" could be treated.
He said he was "sorry" for what he had done.
Judge Peter Testar adjourned the case for six weeks for a psychiatric report.