A senior police officer waged war on illegal scrapyards after spotting a rise in the number of old cars being stolen from Harrow's streets and crushed.

The vehicles, all manufactured before 1998, were being towed away or hoisted onto the back of a lorry before being taken to unscrupulous merchants for destruction and then shipped abroad to cash in on the rising price of metal.

A total of 90 cars disappeared in Harrow in April and May alone. Since Operation Haines - a police sting organised last Thursday by Superintendent Matthew Gardner - there have been no reported thefts.

The operation saw a total of 150 officers, joined by colleagues from local councils, Her Majesty's Revenue and Customs, fire brigades, and the Health and Safety Executive, raid scrap merchants located throughout north west London, the Thames Valley and Hertfordshire.

They went to check that the firms were licensed to operate and to ensure they did not receive stolen cars to crush.

More than 30 businesses received a call from police and 10 people were arrested, although no arrests were made in Harrow.

Half of the firms visited were found to be operating without a licence and of the five unregistered yards discovered in Harrow, three were closed and the remaining two ordered to get licences or shut up shop.

Supt Gardner said: "It's been a good success. It was big: maximum impact with minimum resources.

"We identified the problem and drove this action as a result of what we have seen in Harrow - an increase in the theft of old vehicles as a result of the rise of scrap metal value in emerging economies such as China.

"The thieves don't have to break inside the car. They pick it up with a grabber or tow it away."

He said several months ago, at the beginning of the investigation, officers on patrol in Harrow who had been told to keep a lookout for suspicious lorries carrying old cars on the back spotted one such truck.

They followed the lorry to a scrap-yard in Hertfordshire and arrested the two men delivering the vehicle and the yard owner, who was later found to have £28,000 in cash on site and £490,000 in offshore bank accounts.

Supt Gardner said: "The message is: if you're a scrap metal dealer, get licensed. We will do these visits again on a national basis."