Esther Rantzen has told 100 Jewish Care residents and Holocaust Survivors Centre members that they are "national treasures who deserve to be listened to".
The broadcaster and journalist recently founded the confidential Silver Line service for the elderly. She explained to her audience at Jewish Care's Wohl campus in Golders Green how the helpline had been prompted by her own experiences.
"After my husband died, I was living alone for the first time at the age of 71," she said.
"I wrote about being lonely and the response I got was overwhelming. People told me I was brave to be so honest.
"It was then that I realised that people don't want to admit to being lonely and often have no one to talk to."
At Silver Line, "we get calls [ranging] from those who just want someone to say goodnight to, to more serious cases of abuse and neglect."
Elli Beutel 98, who uses the day centre at the campus, confided: "The worst thing I've faced with getting older is the loss of mobility and independence, and with that comes less social interaction.
"Silver Line is a great idea because it means people don't have to miss out on that."
HSC member Alec Ward said he would use the service if necessary and would recommend it to his friends. Silver Line is currently fielding 500 calls a day.
As part of her visit to the campus, Ms Rantzen looked around Jewish Care's independent living apartments for the elderly and the residential nursing and dementia care facilities.
"If only all elderly housing could be like this," she said. "What is so fantastic about Jewish Care is the sense of community.
"The majority of our calls are from people who live alone and go days without seeing anyone.
"If they knew there were facilities like this available to them - and they didn't think of them as negative options - they may not be so lonely."