A glass box in Churchill Square, Brighton, is being used to try to give people an insight into the loneliness felt by many cancer sufferers.
Macmillan Cancer Support said that it was concerned about the number of lonely cancer patients.
The charity reckons the figure is about 550,000 – about one in five of more than 2.5 million cancer patients in Britain.
It has been taking its “isolation box” – a glass box with two-way mirrors – on tour to help people understand what it might feel like to be alone despite being surrounded by people.
Those trying out the isolation box can hear two personal stories from local cancer patients including John O’Sullivan, 64, from Hove, as they talk about the effect loneliness had on them.
Mr O’Sullivan, who received a diagnosis of neck cancer four years ago, said: “I was so shocked and numbed by what I had just heard that all I wanted was to be able to talk to someone who knew how I felt and could guide and possibly advise me through my forthcoming treatment path.
“There was nobody to talk to who really knew how I felt.
“Even though I was exceptionally lucky to have the fullest support from my lovely wife, daughters and a few special friends, I still felt in total isolation.”
Another local cancer patient, Sara Cutting, had triple negative breast cancer diagnosed last month.
She said: “My family and friends were knocking the door down to be there but I also needed other support. At times I felt very lonely.
“I needed to be able to talk about my deepest fears without worrying those closest to me. This is where Macmillan saved and continue to save me.”
The isolation box is in Churchill Square from 10am to 4pm today (Friday 28 August).
Those inside the glass box can’t see out although people outside can see in. It is intended to evoke the same feelings of loneliness and isolation that many people experience after a diagnosis.
Macmillan said: “In an instant, members of the public are taken from the hustle and bustle of one of Brighton’s busiest shopping centres into an isolated box with just their own reflection and the voices of real people talking about how lonely they felt after being diagnosed with cancer.
“Like so many people affected by cancer, they will be left feeling completely alone in a crowd.”
The charity added that about 8,500 people who are living with cancer in Sussex are currently believed to be experiencing loneliness.
It said: “Research also reveals the devastating impact that loneliness can have on people’s lives, with many forced to skip meals or attend vital appointments alone.
“At worst this can result in people refusing treatment altogether.
“The research, conducted by Ipsos MORI in 2013, found that, overall, around one in six people in Sussex experience loneliness following their cancer diagnosis.”
Rebecca Hawkins, senior development manager at Macmillan Cancer Support, said: “We know only too well that loneliness can have a devastating impact on people’s lives.
“Quite often friends and family find it hard to understand what someone is going through and how utterly lonely a cancer diagnosis can make them feel.
“With 2.5 million people in the UK now living with cancer, we currently can’t be there for everyone who needs us.
“And until we can, we are calling on people to reach out to someone affected by cancer today. Even the smallest gesture of kindness can make a massive difference.”
To help people reach out to someone they know with cancer, Macmillan has launched The Source, a new website full of advice and inspiration on how to offer the support they need, perhaps going to a hospital appointment with them, offering to cook a hot meal or simply providing a listening ear.
Visit www.macmillan.org.uk/source for more information.