Britain's quarantine laws were waived to allow William Dowell, from Coniston, Cumbria, to bring his dog back from France - the first pet to enter the country legally without undergoing six months' confinement since 1901.
William had been undergoing medical treatment in Lyons when he was given the Pyrenean mountain bitch.
He was distraught at the prospect of the six months' quarantine for his pet on entry to the UK and wrote to the Prime Minister, who made arrangements for Cassis to enter Britain under the "Passport for Pets" scheme, which comes into force next year.
On hearing that she could go straight to the family home, William said: "I want to say thank you very much for my exemption and that I hope the reform is speeded up so that all the cats and dogs that are in quarantine, or have to go into quarantine, are released as soon as possible."
William, who received a kidney transplant in France and treatment for cancer, added: "She's a member of my family and she's been a great companion and is always there for me. I don't know how I'd live without her. I think she understands when things aren't all right with me when I have to go to hospital.
"I don't think she would have coped in quarantine. When I've come out of hospital only after a week, she goes mad jumping up on me. So I don't know how she would cope. She's vaccinated, she's not got rabies, she's safe. She certainly cheers me up when I'm upset and she's my companion."
The "Passport for Pets" initiative is a Government project under which all animals will be checked before travelling to the UK.
William, travelling with his mother, Helen, and brother Jonathan, 14, arrived from France on the Eurotunnel train.
Cassis was checked by a Ministry of Agriculture, Fisheries and Food veterinary inspector at the UK frontier control in Calais/Coquelles before joining the train.
This involved checking an ID microchip, that the dog had been vaccinated against rabies, that drug testing had been done to check the vaccine's effectiveness, that the dog holds a health certificate and that it has been treated against certain parasites.
The family were met at Folkestone by Lady Fretwell, chairman of Passports for Pets. She said: "We have been fighting for many years for the quarantine system to be reformed and it is great to see a healthy pet animal entering the UK without having to go into kennels for six months.
"Cassis is the first, but by spring 2000, thousands of pet owners will be able to return to the UK without putting the animals into quarantine as long as they have been microchipped, vaccinated and blood tested."
Chris Laurence, chief veterinary officer of the RSPCA, said: "Scientific evidence and the experience of other countries around the world shows that vaccinating animals against disease is just as effective and more humane than locking them up for six months."
The pet passport system will apply to animals entering the UK from western Europe or from rabies-free islands after they have been vaccinated against rabies, blood tested, microchipped and given a health check before entry. The Government is also considering whether to include the United States in the scheme.Reuse content