"You often don't know what you've got until it's gone," said clinical nurse specialist, Tracey Slater.
"People often compliment us and tell us what a great job we're doing.
"And now we need their support more than ever."
Tracey is one of a number of volunteers who sacrifices her Friday and Saturday evenings to work on Norwich's SOS Bus.
The service, which operates from the bottom of Prince of Wales Road between 9.30pm and 3.30am, provides vital nightlife assistance to anyone in Norwich whose wellbeing is at risk.
But now the future of the Bus is under threat due to NHS funding cuts.
"I moved to Norwich about a year ago," said Tracey.
"One night around Christmas 2021, I got a call at 3.30am to say my son was on the SOS Bus.
"We just thought he was drunk, but the alcohol had mixed with medication he was taking at the time.
"Someone found him off the beaten track and brought him here.
"That's when I decided to sign up."
Last year, the SOS Bus - which is run almost entirely by volunteers - helped 2,623 people.
Some 205 of those attended with injuries and 33 needed help with their mental health.
It is estimated that 160 ambulance call-outs were prevented, saving the NHS more than £123,000, and 107 A&E visits were avoided, saving more than £34,000.
"If we weren't here, people would be piling up outside A&E," said Paul Dodson, a paramedic of 43 years.
"We can get call-outs to people collapsed in the street from minute one.
"We serve as a safety net that helps to ease the pressure on the NHS."
For the last four years, Voluntary Norfolk has been providing the gap in resources - with funding failing to cover the costs of the Bus, even with donations from members of the public.
And now local health service chiefs are believed to be weighing up whether the service is surplus to requirements - with the new wellness hub that opened in Castle Quarter this year potentially expanding.
"There is quite a bit of misunderstanding about what we do," said Belinda Buxton, a volunteer for more than 10 years.
"People seem to think we're just the drunk bus. But we're so much more than that.
"We help with accidents, medical problems, assaults and mental health.
"If needed, we take people to A&E and sometimes even drive them home.
"We have support staff who will drive to call-outs from clubs or venues and bring people back here who need our help.
"We'll also charge mobile phones and offer flip flops to stop people hurting themselves on nights out.
"If someone needs our support we will stay with them until a responsible carer picks them up or we are confident they are okay - even past 3.30am.
"We wouldn't just kick someone out who's vulnerable."
The big, yellow SOS Bus was launched in April 2001 after the tragic deaths of Nick Green, 16, and James Toms, 21, in the River Yare.
Since then, it has become a staple of Norwich's nightlife scene.
"This is an incredibly important service," said volunteer Tim Lukosevicius-Spooner.
"It's a non-judgemental space that supports people when they need it most.
"I have a daughter and knowing something like this is here just makes Norwich safer."
The Norfolk and Waveney Integrated Care System launched a public survey last month about the future of the SOS Bus.
It claims no decisions have been made about closing the service.
"We are inviting people to share their feedback and experiences to ensure that the SOS Bus meets the needs of those who have used it," a spokesman said.
"The Wellness Hub is keen to develop the services it currently offers."
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