When a Panorama team went undercover on Merseyside posing as a new security firm, their arrival was not welcomed by rivals.
Panorama: Britain's Protection Racket, BBC One 8.30pm Monday 21 January 2008
The hostile reaction confirmed that Britain's £7 billion security industry is still scarred by a culture of violence and intimidation.
An industry insider told Panorama that Liverpool was a city bedevilled by rogue security firms.
The programme set up its own security company. Would-be security guards went round the city handing out business cards and trying to persuade businesses to switch their security contracts.
But some firms do not take kindly to competitors or welcome any potential clients refusing their offers of service.
Chief Supt Andy Cooke of Merseyside Police said: "People have had guns put to their head.
"We've seen extremely serious arson attacks where an awful lot of damage has been caused...
"These people seriously affect the standard of living of everybody."
The police and the Security Industry Authority, which regulates, vets and licenses firms have both got tough with the rogue companies launching Operation Seahog targeting rogue firms across the city.
But Chief Supt Cooke said: "We have arrested people for blackmail, for extorting money from other security companies as part of our covert approach to what we're doing.
"We've recovered firearms, we've recovered drugs, we've recovered enormous amounts of money and assets from companies."
He said people felt intimidated: "It's all very much implied in the visits they do, and the letters they write, in their approaches to companies themselves.
"So there won't be any direct level of intimidation, it'll just be quite simply 'this is our area and we'll provide your security'"
One Church of England vicar found out just how intimidating some of these firms could be.
Shannon Ledbetter runs the Liverpool branch of Habitat for Humanity, an international charity based in Toxteth. It helps build homes for low-income families.
A number of security firms visited the charity's building site offering their services.
When their services were declined - there was a fire. The police were in no doubt it was arson.
"It was devastating for me personally but it was also a representation of the destruction of hundred's of people's efforts. It was gut-wrenching really," she said.
And what of Panorama's own security firm?
The new kid on the block received no shortage of warnings as its leaflets were being delivered.
Said one person: "These are gangsters. They basically turn round and say 'we're doing your site and if we don't we're going to beat you up'."
Another said: "You wouldn't want to be stepping on these boys' toes really. They are not nice."
Panorama: Britain's Protection Racket, BBC One 8.30pm Monday 21 January 2008.