A new COVID-19 antibody test is "100% accurate", according to England’s public health body.
Public Health England said the new test – devised by Swiss pharmaceutical company Roche – had now been assessed and approved.
The blood test determines, via the presence of antibodies, whether a person has already had the new coronavirus.
The antibodies are a reaction by the immune system to an infection.
However, there is no guarantee at this stage that their presence excludes the possibility of re-infection.
Health officials had not considered the previously-available testing options to be reliable; they reportedly gave a number of false positives and false negatives. The UK government was said to have spent £16 million (€18m) on these unreliable methods.
Meanwhile, preliminary results from a nationwide antibody study in Spain suggests that only about 5 per cent of the Spanish population have contracted COVID-19
The fact that only 5% were found to have antibodies present in their blood samples means the country is far from the point that it might seriously consider widescale de-escalation of the lockdown restrictions.