- By Jamie Roberton, Chloe Keedy, Chris Howse and Natalia Jorquera
It has been described as a public health emergency; a silent epidemic as lethal to our health as smoking and obesity; a problem deserving of a dedicated government minister.
As part of a special week of coverage examining the issue of loneliness, we have spoken to the people - young and old - in crisis behind closed doors.
From young Edward to widow Angela, we meet Britain's many faces of loneliness - and examine possible solutions.
- Angela, widow
Meet Angela. She's 85 and recently lost her husband of more than 60 years.
"I feel very lonely at times," she told ITV News.
"I watch television because that's sometimes the only company I have. But when something comes up and I say, 'Oh look at that' - thinking my husband is still there and he's not - that's when it hits you really hard."
She added: "Sometimes I just sit and cry."
Angela now attends a new adult day centre in the Oxfordshire town of Witney, where she enjoys lunch and plays games with new friends.
"Coming out here is something to look forward to as everyone is so caring and kind and friendly."
- Edward, a young carer
Edward is one of 700,000 young carers in the UK.
The 11-year-old, who helps his mother and father care for his sister Amelie, who has significant learning difficulties.
While his parents are Amelie's main carers, Edward's commitment to helping his sister has often led him to feeling torn and isolated.
"I can't really plan days out with my friends because I have to be looking after Amelie and helping my mummy and daddy."
Edward now visits his local Carers Trust centre to socialise and for time to make new friends.
With an estimated 89% of carers across the UK having experienced feelings of loneliness and isolation, Edward wants society to start caring for the carers.
- Amy, new mum
Amy Nickell was 24 when she had her son, Freddy.
As a single mum, Amy said she couldn't afford rent and childcare - so she had to give up work and move back in with her parents.
"When he was born, I felt like I was having my maturity and adulthood taken away from me, because suddenly I was living back at home with my parents and I felt like all my independence had dissolved," she said.
In her previous job as a red carpet reporter, Amy was "constantly surrounded by people". She said "suddenly finding herself with only a new born baby for company was a bit of a shock to the system."
Unable to see as much with her old friends anymore, Amy also didn't feel like she fitted in with the other 'mums', who were older than her. It left her feeling isolated.
- Angel, student
When Angel came to London to start university, feeling lonely was the last thing she expected.
She found it hard to make new friends, and says seeing what everyone else was up to on social media just made her feel more isolated.
"I was literally going to class every day, coming home and sitting in my room. At weekends I would just go home because I had nothing else to do, or sit in my room and watch TV."
Official figures show that the loneliest people in London are not the elderly -but the young.
Nearly a quarter of 16-24 year olds feel lonely some of the time, while 10% say they are lonely 'often' or 'always'. That compares to 3% of people over 75.
- Don, retired
Don, 86, started attending cooking classes when his wife fell ill.
"I was looking after her and it gave me a break in the day to come here for a couple of hours and then to cook," he recalled.
"It didn't matter what I was taught, she passed away from pancreatic cancer, sadly."
He is one of the many people up and down the country who use cooking classes run by Age UK Barnet as a way to help combat isolation.
Nancy, who runs the sessions, says the classes have helped cultivate and nurture countless friendships over the years.
"The idea is to get men to socialise, but with a task. I think they get out, learning a new skill, they have company - it combats people's isolation if they are a bit lonely. They have fun and they just thoroughly enjoy it."
As he enjoyed his latest cooking task, Don told ITV News: "Oh no, it's not just about the food. What I most enjoy about these classes is the camaraderie."
- Meet the G&T trio
With a six decade age gap, Seb, Neil and 95-year-old Christine are the unlikeliest of mates.
But since the trio met through a Contact the Elderly scheme four years ago, they have become the best of friends.
Most Sundays, they head to a local London pub and play scrabble over a gin and tonic.
"It was a lucky day when I met these two - they've made quite the difference to my life," Christine told ITV News.
- The robots helping children beat loneliness
Long term illness is often another cause of loneliness but one company has found a way to help housebound children beat the feeling of isolation in the shape of a robot.
Fitted with a camera, microphone and speaker it acts as a child's eyes and ears in the classroom - streaming live pictures to their tablet or smartphone at home.
ITV News London travelled to Oslo to meet the robot's makers who say it helps children feel part of everyday life.
- Why day centres are so crucial to so many
Adult day centres are considered a vital lifeline to the elderly and vulnerable adults like Angela, who can otherwise be left isolated at home.
But an ITV News investigation has revealed the dramatic scale of day centre closures by cash-strapped councils since 2010.
Critics said the figures, obtained through a freedom of information request, undermined Theresa May’s commitment to tackling loneliness as her government prepares a strategy to combat the issue.
Useful numbers to call:
- Contact the Elderly are dedicated to tackling loneliness and social isolation among older people - find out more about what they offer and how to become a volunteer: 0800 716543
- The Carers Trust works to improve support, services and recognition for anyone living with the challenges of caring. Find out more here