A test rated by experts in Wiltshire to determine whether or not people have had coronavirus is 100% accurate, according to Public Health England.
Scientific experts at PHE's Porton Down facility have been conducting evaluations of a new antibody blood test developed by a Swiss pharmaceutical company.
Their examination found it is "highly specific" and 100% accurate.
Prime Minister Boris Johnson has previously said an antibody test could be a "game-changer" in the easing of lockdown.
The test is designed to help identify people who have had Covid-19 without any symptoms, and so may have gained immunity against it.
Professor John Newton, national coordinator of the UK Coronavirus Testing Programme, said it remains unclear to what extent the presence of antibodies indicates immunity to the virus.
But, he continued, it is a "very positive development" which could in turn "indicate some immunity to future infection".
This could prove a significant development in getting people back into offices across the West Country, confident that they are unlikely to contract the virus.
The great thing about having a test to see whether you've had it enough, is suddenly a green light goes on above your head and you can go back to work safe and confident in the knowledge that you are most unlikely to get it again.
A Department of Health and Social Care spokesperson said: "We are exploring the use of antibody testing across the NHS and ultimately the wider public.
"We are delighted that devices are progressing through validation, and areactively working on our plans for rolling out antibody testing and will makeannouncements in due course."
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