In some of the borough's wealthier streets a perception that burglaries, muggings and car crime are on the up has driven residents to pay thousands of pounds a year for private security companies.

Companies that can station a security guard on a street throughout the night are charging upwards of £50,000 a year, with hundreds of residents apparently happy to pay for peace of mind.

Steven Novak, 42, of Uphill Road, Mill Hill, has organised security on his road through Hendon-based 1st Class Protection, which charges 100 residents approximately £100 per month for a security guard to patrol the road in a car every night.

The guard looks out for suspicious behaviour and can be called to meet and escort residents to their doors at night.

Mr Novak said: "Of course it's a shame we had to have it but it was just getting unbearable. The security isn't going to cut crime out completely, but it makes a massive difference."

The fee is commonly shared between a residents' association formed specifically for the purpose, which makes it easier for companies to deal with them.

"We're fortunate because there are so many of us paying for it," said Mr Novak. "In other areas you might only have five households paying for it so they would have to pay thousands more."

Assaf Cohen, a former Israeli army specialist operations officer and managing director of 1st Class Security, said his company has guards stationed permanently in two streets in Mill Hill, as well as two more in Hendon and Edgware.

"We're usually brought in after there has been a serious incident," he said. "It's easier for residents to see why it's needed after that.

"Most of the job is about being a deterrent. When criminals see our guards they'll move to another street.

"Some of the criticism is that we don't prevent crime, we just move it, but every person has the opportunity to protect his family and that has to be your first priority. If it moves it to the neighbours, well, they have to protect their own family."

He also said that his company is receiving an increasing number of calls from residents in the borough.

"Police say it's more the fear of crime that is increasing, but I'm not sure I can agree with that."

Mr Cohen's assessment conflicts with Met police figures, which indicate that crime in the borough has fallen in successive years.

However, burglary has risen in some wards.

Another company, called London Community Services Ltd (LCS), started patrols in Hampstead Garden Suburb five years ago and has expanded to cover parts of Finchley and Hendon.

Operations director Peter Williams would not reveal how many streets or individuals are now using the service, but said that demand was increasing.

All guards employed by security companies have to be trained to a minimum standard and be registered with the Security Industry Authority, which regulates the industry.

David Marks is chief executive of SectorGuard, a Hertfordshire-based company which protects one wealthy street in Monken Hadley full-time and has taken on several other temporary contracts in the borough in the past two years.

He said: "Unfortunately, it's a sign of the times that people feel they have to supplement the police service.

"If you can afford to have better security, why wouldn't you have it? Especially in light of headlines about burglary and street crime."

He said his company is particularly useful for streets specifically targeted by criminal gangs.

"People get nervous and the police can't provide a solution for that one street. That's where private security companies can fill a void."

The police declined to comment on the issue.