Greek engineer Ioannis Revenikiotis, 28, fled his home in Dewsbury after he abducted and killed the 20-year-old travel agent, who thought she was getting into a taxi.
But he was travelling in a black Mercedes C180 matching the CCTV pictures of her abductor's car and at Dover his car registration was picked up by cameras able to read car number plates.
They are linked to databases showing stolen or un-registered vehicles or those which have been involved in crime and enabled police to discover his route.
Now statistics provided by the region's four forces following a Freedom of Information request reveal the so-called Automatic Number Plate Recognition (ANPR) system has been hugely successful in tracking down people wanted for a host of crimes.
Last night it was hailed as an important tool for snaring offenders, but critics warned it was important databases were kept up-to-date to prevent innocent people being stopped wrongly.
In West Yorkshire 4,173 people have been arrested from when the system was introduced in October 2002 to July this year. The largest number, 880, was for driving offences but there were also 557 for theft/burglary and 279 for drug crime.
Other car-related crime accounted for 598 arrests, while those wanted on warrant numbered 681.
The force has spent around £875,000 installing the system, including about £175,000 on putting it in police traffic vehicles and about £300,000 on adapting CCTV in Wakefield, Leeds and Bradford to use the system.
North Yorkshire Police have arrested 1,070 people from when it was introduced in June 2003 to June this year. The arrests covered a similar wide variety of offences.
The force spent £790,000 on creating an ANPR team, inc-luding the cost of staff and purchase of vehicles. The team has a £540,000 annual budget to cover salary expenses and running costs.
South Yorkshire Police reported they had recovered 33 stolen vehicles since they introduced the system in October last year. A further 243 vehicles were seized be-cause drivers had either no insurance or driving licence.
A total of 270 arrests were made and a further 1,056 offences reported for summons. The variety of crimes included immigration offences, counterfeiting, assault and the carrying of offensive weapons – as well as the broader categories like burglary or drugs. The force received £300,000 from the Home Office to pay for installation of the equipment.
Humberside has to date carried out 296 arrests since installing ANPR in January 2005, with money-laundering featuring on the list of offences involved.
The force paid £350,000 to have the system installed, with maintenance costs of £30,000.
All four forces reported they had not received any complaints from the public about the use of ANPR.
A spokesman for the AA Motoring Trust said that while the technology was very useful it was important the databases holding information on vehicles were kept as up-to-date as possible to minimise the numbers of drivers stopped wrongly.
But John Dean, national co-ordinator of ANPR technology for the Association of Chief Police officers, said: "I think it's fast becoming a core policing tool. I think it's
fair to say it is the finest intelligence-led policing tool we currently have.
"It helps focus police officers on people who are of interest to us, either wanted criminals or those suspected of being involved in crime, and that in turn means law abiding people using the roads are not hindered by the police.
"It is ACPO's aim to deny criminals the use of the road."
The road safety charity Brake said ANPR cameras were a crucial tool in
helping the police spot irresponsible drivers, in particular those without insurance who are responsible for a significant number of accidents.
A spokeswoman said: "Brake welcomes the use of ANPR technology and believes that this is the right step towards catching
and stopping people driving illegally on our roads. Brake would like to see ANPR used extensively throughout the UK, with all forces carrying out more random stops and checks of suspect vehicles."
n Revenikiotis, 28, was ordered to be detained indefinitely under the Mental Health Act on Thursday after he was found to have kidnapped and killed Ms Hammill.
She died on November 29 2003 in Wakefield when she jumped or fell from his car and was hit by a taxi travelling in the opposite direction. He was eventually tracked down in Greece, where his car was found in a scrapyard.


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