A "drunks-only" ambulance is mobilised on occasions of widespread drunkenness in central London. What's it like aboard the "Booze Bus" on one of the busiest party nights of the year?
By Alexis Akwagyiram, BBC News
"I love the job - I like being able to make a difference. No two days are ever the same," says paramedic Brian Hayes with a jovial grin as he describes his job.
Over the course of a 12-hour shift on Friday night, he and his two colleagues on the Alternative Response Vehicle - or Booze Bus, as it's more commonly known - draw on their reserves of composure, ingenuity and stoicism to treat more than 20 dazed drunks.
At St Thomas' Hospital, where some of these patients are taken, a visibly-frustrated doctor speaks despairingly of dealing with a tide of alcohol-related problems, instead of people who are seriously ill.
"Everyone I've treated tonight has been drunk - this is ridiculous," he says.
At about 0200GMT, he predicts things are only going to get worse as the night goes on.
"I have no beds in my observation units as we're full already. This is the calm before the storm - it'll go ballistic."
One drunk patient had assaulted him, he says, and the waiting room was full of people being sick or aggressive.
"Twenty-four hour drinking has made a huge, huge difference. The problem is that staff are dealing with people who are drunk and don't know what they're doing," he says.
"Doctors are run off their feet and in the vast majority of cases it is just alcohol. It is binge drinking. We don't see people who've had just two drinks. People have had 20 shots of vodka.
"They're generally 18 to 25, but it's all sorts - including lawyers and people in their 60s."
An hour later the stench inside the ambulance is thick and overpowering after three patients have been picked up.
The smell of stomach bile, excrement and stale urine fills the enclosed space as the vehicle speeds through the West End streets.
A scantily-clad 21-year-old woman lies motionless with one arm attached to a saline drip. She was found lying unconscious near a West End club and taken inside by a doorman.
Her stockings sag limply around her ankles and she occasionally stirs to vomit into a tray, her eyes opening briefly and rolling towards the ceiling.
On a seat next to her a man in his early 30s is being attended to. He was found unconscious in a corner of the same nightclub suffering from the effects of a cocktail of drink and drugs.
Another seat is occupied by a 60-year-old man, found outside Holborn Tube station, whose silver hair is matted with a layer of thick, crimson blood. He is slumped, with a steady trickle of saliva dribbling down his chin. The man has soiled himself.
The Booze Bus - or Vomit Comet, as it has also been dubbed - was Mr Hayes's creation three years ago. The three paramedics take the alcohol ambulance out at times of heavy drinking, such as the World Cup, Gay Pride and the festive season. On a busy night it treats more than 20 people.
"The idea was to make everyone's life easier and make handling Christmas drinking more manageable," says Mr Hayes, 37.
"Normal ambulances are freed up to do work that matters and can save lives. It also means there's a hospital bed free."
Unlike other ambulances, it does not carry an ECG machine because it won't need to treat chest pains and the extra space can be filled by a patient.
It can take up to five patients to hospital in one trip - if no-one is seriously injured - rather than sending multiple ambulances.
On a Friday night in mid-December, with Christmas office parties in full flow, Leicester Square and Soho are packed with revellers, increasing the demand on London Ambulance Service by 10 to 15% compared to a normal Friday.
Mark, a civil servant manager in his 40s who had been drinking since 12 noon, found himself slumped over his Chinese meal due to one such party - prompting his colleagues to tie him to a chair and carry him out of a restaurant.
And there was Sally, a 24-year-old accountant, who was struck by a glass which was either dropped or thrown at her firm's festive celebration and left a shard embedded in her forehead.
Meanwhile, Stephan, a Swedish special effects technician broke and dislocated his ankle after climbing over railings to get into Soho Square Gardens after drinking at least seven pints at his work party.
But 18-year-old James bucked the party trend and was instead a victim of pure violence. He was found wandering around Leicester Square shirtless, with one shoe and a bloodied face after being set upon by more than a dozen youths.
Throughout the night and early hours, the three crew members exchange rapid-fire banter and remain upbeat when faced with a procession of bleary-eye patients in all shapes, sizes and ages.
"It's about being tolerant. Most of the people we deal with have been vomiting on themselves," explains Mr Hayes.
But he adds: "It scares me that these young girls are getting into nightclubs. There is a massive problem with underage drinking.
"I don't know what's happening to society as a whole. It's scary - it's not just the kids. It's also adults. People in their 40s and 50s who you would think know better.
"But then you get a job where you make a massive difference, and you feel much better."