Christmas dinners have been served to Londoners who are reliant on the city's homelessness services.
Hairdressers and opticians were also made available at City Hall before guests were given a three-course meal.
Last year, 8,855 people were seen rough sleeping in London, an 18% increase since last year, and more than double the number in 2010.
"Events like this help bring a sense of community back in to London," Claire, a former rough sleeper, told the BBC.
Claire, who spent 30 years either living on the streets or in prison, said: "It's the type of event that does matter. It forms partnerships and builds bonds.
"If it wasn't for the support of St Mungo's, I'd either be dead or doing what I was before."
Guests were chosen from the thousands of Londoners that currently receive assistance from services funded by City Hall and delivered by charities St Mungo's and Thames Reach.
But Claire said services were still "hit and miss".
"Where I live I'm still waiting for support with my mental health," she added.
Mayor of London, Sadiq Khan, said: "St Mungo's and Thames Reach are struggling with finances.
"Since I became mayor we've more than doubled the amount of money we've spent on rough sleeping and the size of our outreach team.
"But we're just scratching the surface. We've not got the money or the resources to do much more - as it is I'm criticised for going outside my remit and my power.
"It is both heartbreaking and shameful that in one of the richest cities in the world we still have the levels rough sleeping that we do."
Last year 15,470 people were accepted as being homeless by London councils.
There were 55,000 families living in temporary accommodation, such as bed and breakfasts and hostels.
Hundreds more people are estimated to be sleeping on London's night buses.
Petra Salva, Director of Rough Sleeper Services at St Mungo's, said: "It's wonderful that the Mayor has opened the doors of City Hall for this festive event.
"Christmas can be a time of mixed emotions for clients in our services and our staff work hard to support those who stay with us over the holiday period."