By the time the paramedics arrived at Kathy Ceaton’s home she was dead.
Police are investigating the incident involving the driver of a silver Vauxhall Astra who refused to move over for the emergency vehicle and then made obscene hand gestures.
Ms Ceaton, 66, was the mother of Hollywood producer Matthew Vaughn, who has three children with supermodel Schiffer, 42.
She is thought to have died from a heart attack.
There is no indication that the delay caused Ms Ceaton’s death. But Vaughn’s step-brother Pasha Saigol, 32, hit out at the driver who hindered the ambulance.
He said: “I have been told it would not have made any difference to my mother as there were paramedics on site.
“But I do take issue with it from a moral standpoint. People should not be blocking any emergency vehicles.”
An official statement released yesterday on behalf of Ms Ceaton’s devastated family paid tribute to a “generous and loving” mother. It said “her intelligence, generosity, loyalty and friendship will be missed by many”.
A date has not yet been set for her funeral.
Just after 12pm last Sunday friends of Ms Ceaton called paramedics to her home in the Oxfordshire town of Thame.
A rapid-response car was despatched along with a helicopter and a pair of ambulances.
The Astra blocked one ambulance as it drove through the village of Haddenham, near Aylesbury, a spokesman for South Central Ambulance Service said yesterday.
“One of the ambulances was unnecessarily delayed due to another road user who refused to pull over and allegedly made rude gestures at the crew.
“We have informed Thames Valley Police and are obviously seeking a prosecution for obstructing an emergency vehicle en-route to an emergency,” he added.
Sgt Ian Baldock of the force’s roads policing unit called for witness to come forward.
He added: “We have identified the car involved and are carrying out an investigation to establish the full circumstances.”
Matthew Vaughn, 42, was born while his mother was living with Seventies screen legend Robert Vaughn. But the star of The Man From Uncle and Hustle has denied being the Lock, Stock And Two Smoking Barrels producer’s father.
Ms Ceaton later married Pakistani industrialist Javed Saigol.
The ambulance trust has posted a Blue Light Aware video online to show the public how best to help emergency service drivers.