Conceived in New York, the Guardian Angels' unique brand of law enforcement never really caught on among London's reserved commuters and volunteer numbers have dwindled. But will the London bombings help finally endear them to us?
Sedleigh "Shaft" Adams signals his red-bereted patrol to move on to the Tube. Once in position he scans the carriage until, eventually, he catches a mistimed glance.
"Never smile at a Guardian Angel," he says. "That means you have a pulse, and if you have a pulse then you get a leaflet."
Sweeping through the carriage he then hands out leaflets to the bemused commuters headed: "SOMEBODY REALLY SHOULD DO SOMETHING ABOUT VIOLENT STREET CRIME!!"
The Guardian Angels (GAs) have become a familiar part of urban folklore since being founded in New York in 1979 by Curtis Sliwa. A McDonald's night manager in a crime-infested part of the Bronx, Sliwa decided to form his own street patrol.
From a voluntary, unarmed band of 13 men grew a 1980's phenomenon, with chapters now patrolling streets across the world in the spirit of their motto "Dare to Care".
The Angels said to me it's all about having the right attitude, and since then I must have because I've stayed out of trouble
But the London chapter, founded in 1989, has fallen on hard times. It is now kept alive by just 12 volunteers on a shoe-string budget, making it difficult to train new recruits and promote experienced members.
Patrick "Dreadzone" MacRodain has been a GA since 1998 and is one of the London chapter's most experienced members.
"I should have three chevrons on there," he says, sounding slightly disappointed as he points to his red beret.
He credits the organisation with helping transform a life spent in and out of custody as one of the "bad boys of Hackney". MacRodain joined up after the GAs intervened as he tried to help a man being attacked in King's Cross in 1996.
"My life turned around after that," he says. "The Angels said to me it's all about having the right attitude, and since then I must have because I've stayed out of trouble and I'm up for promotion to patrol leader."
Nowadays, he dons his beret to escort pensioners on their way to paying their rent and also plans to speak at schools to encourage children to avoid the traps he fell into.
Everywhere they go the patrol is well received by London Underground staff and an intrigued public, albeit at times with thinly-concealed amusement.
On patrol with the Guardian Angels
"I think they're mental," comments one passer-by. "I grew up in New York in the 80s and haven't really thought about them since then."
In Shoreditch - a fault-line between the opulent City and some of London's most deprived areas - licensee Jonathan Moberly welcomes the GAs patrolling outside his busy bar.
"It's all good having them around," he says. "With the new licensing laws and security threats we're in danger of becoming both under-policed and over-policed at the same time."
Mr Moberly believes the GAs have the potential to fill a gap in community policing.
"How do you control problems? You talk to people and treat them like people. That's what the Angels represent, their message is let's not get too uptight about it and bring it back down to the ground," he says.
But the boys in berets have a less harmonious relationship with the police, who resolutely refuse to recognise the organisation. After the 7 July bombings in London Adams admits they had to consider whether they were a "help or a hindrance" during heightened security.
However, he says the public greeted their patrols with a "heightened response" and were "increasingly pleased to see us".
At ground level, though, it rather seems as if the GAs have had the rug pulled from under their feet. Asbos, council-run street warden schemes, community support officers - all have sprung up since they arrived in London 16 years ago.
Adams denies such measures have made his team an irrelevance.
"There is a distrust of authority that means that the CSOs' police-style approach can't get close to communities, especially ethnic minorities that traditionally have a poor relationship with the police," he says.
"It's like the difference between classical and rap music. Kids don't want to hear classical, they want to hear rap. So you use rap music to draw their attention.
"When I look at what's called the yob culture, those kids have got so much street skill. If you can harness these skills then the kids can make something of themselves.
"But if the Metropolitan Police force can't manage that on a multi-million pound budget then we don't have a chance... or do we?"