Danielle Cable, spent 12 days with a team of Spanish and British detectives pretending to be tourists in resorts on the Andalucian coast .
Mr Noye was arrested on Friday in connection with the "road rage" stabbing of Stephen Cameron on the M25 near Swanley, Kent, in 1996. Ms Cable, then 19, was with her fiancee when the incident happened.
Mr Noye was caught after a month- long surveillance operation by British and Spanish police. He was arrested after being spotted dining with a woman at a remote pizza restaurant, Il Forno, in the mountain village of La Muela near Cadiz.
In a highly unusual move, Ms Cable had been flown to Spain to help carry out surveillance on Mr Noye.
The officers spent a fortnight tracking Mr Noye as he went about his business as a jobbing builder. They even watched him help a girlfriend unload furniture and move into a tiny beach-side cottage in Canos de Meca, another of his favourite vocations in his southern Spanish hideaway.
Once detectives were convinced he was their man, they flew Ms Cable to Spain. She spent 12 days with the joint team of Spanish and British police officers posing as tourists at the resorts of Barbate and Zahara de Los Atunes.
Spanish workmen employed by Mr Noye in his burgeoning construction business were stunned to hear of his real identity. Yesterday, they turned up at the villa at Atlanterra where Mr Noye had been living and which he was refurbishing.
It emerged yesterday that he was using a British passport in the name of Alan Edward Green which was issued on 3 December 1996 with a date of birth of 27 January 1956.
An optician stated that he had been treating Mr Noye for long-sightedness for the past two years while he had been staying locally - which contradicts various alleged sightings of him from Northern Cyprus to Russia.
Lawyers acting for the Crown Prosecution Service, as well as diplomats, were doing their utmost to clear the paperwork necessary for Mr Noye's extradition, said Patrick Owens, a spokesman for the British embassy in Madrid. The British Government has 40 days to begin extradition proceedings.
Mr Owens said: "We hope this stage will be cleared rapidly. Everything that has happened so far suggests that there will be no delays and that this matter is being taken very seriously by both British and Spanish officials. Once the final signatures from the Spanish cabinet are received on the extradition papers, Kenneth Noye will be rapidly sent back to Britain."
But local lawyers said extradition could take at least 10 months.
Unless Mr Noye agrees to go back to the United Kingdom, it will take at least six months before the case is heard in Madrid at the Audencia Nacional - the central criminal court. If extradition is granted, Mr Noye can appeal to Spain's Supreme Court, which could take another three months.
He is currently being held at the maximum security prison in Puerto de Santa Maria, near the provincial capital of Cadiz, where he will be visited today by Carlos Formby, British Consul in Seville.
Mr Noye disappeared from his home in Sevenoaks, Kent, after the stabbing and detectives had no idea of his whereabouts until a tip-off by a British holiday-maker a month ago.
Mr Noye had spent his time in Spain buying and renovating villas, which he sold for profit.