Blood tests taken up to four weeks ago have revealed that the person did catch the deadly flu bug.
But because there was such a gap between the blood being taken and the result coming through, the person has now got better.
The patient, whose identity is being kept secret, has been told about the result.
Doctors say there is no need for further action because the patient doesn't appear to have passed on the virus to anyone.
Around 160 suspected cases of Sars in the UK have been reported to health officials.
Most people turn out to be suffering from flu and other infections.
There have been 7,628 probable cases of Sars worldwide and 587 people have died from the virus.
Most of the cases have been in Asia. The outbreak started in southern China in late 2002.