More than 14,000 music fans filmed themselves taking Covid tests so they could get into a festival, as part of a scheme using video to get into mass events.
Bosses at the Standon Calling in Hertfordshire, which boasted artists including Bastille, Craig David and Primal Scream, insisted that no one would be allowed in unless they could verify they had tested negative for coronavirus.
So around 14,865 music lovers agreed to record themselves doing lateral flow tests in order to be allowed into the festival last month - and just 40 tested positive.
Clips were uploaded onto an app, which were then verified to make sure ticketholders were being honest and had done the swab correctly.
If all was in order, festivalgoers were then sent a QR code, which gave them access to the site. The process cost each user £4.
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Dr Jack Kreindler, medical director of Certific, the company that carried out the verification - said he was surprised that it met little resistance among those attending the festival, saying it is a sign people do want to help each other out.
So-called certification apps may become an important tool in helping to allow such large events to take place safely, it is claimed.
Dr Kreindler told The Mirror that verifying people do the test properly would also bring out more reliable results.
"People can say that they've gone a lateral flow test, but there's absolutely no way of checking they'd done it right," he said.
He said the future for certification apps will depend on whether vaccines can beat the virus and if rates plummet, but he added: "To keep industry open it may be necessary to make sure there's more certification.
"It's very inexpensive to use this technology."
He said it took a team of 14 experts employed by Certific to review clips uploaded by nearly 15,000 music fans.
He said that while data identifying individuals is deleted as soon as checks are carried out, findings from the weekend will be invaluable in working out how large events can run safely in future.
Dr Kreindler continued: "We know that around 40 positives were found, and they wouldn't have been found otherwise.
"What we definitely do know is that with finding these people using the NHS testing system, if they were young and unvaccinated they'd have given it to a lot of people.
"This isn't a clearance system, but it will help to make it a bit safer."
He said, however, that using lateral flow tests will not pick up 100 per cent of cases.
More than 95 per cent of those attending went through the verification process, which everyone else taking a lateral flow test at the entrance to the festival and having to wait for the results.
Dr Kreindler said he was stunned that so many people had agreed to take part.
"We were very very surprised by the number of people who co-operated fully in the process," he said.
"We're seeing that the vast majority of people do go through extra hassle to help each other out.
"If technology and science is helping to do that, we're on the right track."
Outlining the advantages of verified testing in a paper published in the Journal of the Royal Society of Medicine earlier this year, Dr Kreindler and colleagues from Imperial College London and the University of Tartu wrote: "Briefly, once an event is announced, the customer would purchase a ticket to an event, which would become valid only after they complete a risk questionnaire and complete a home test.
"The test would be videoed or live streamed to a professionally trained testing control officer, allowing for near-real-time assessment validation of the patient and test kit identity, and validity of the test result depending on the assessment of the sample collection method.
"Ticket holders that show a positive result would be alerted and will quality for an automatic full refund of the ticket price and the corresponding ticket marked as invalid and notification given to public health authorities."
It is not yet known how much large events are contributing to the spread of Covid-19.
The same weekend as Standon Calling, the Latitude Festival attracted 40,000 people in Suffolk.
It was part of the government's event research programme, which is monitoring the impact of gatherings such as festivals.
Everyone attending had to show proof of a negative lateral flow test within the previous two days, or proof of full vaccination.
Stuart Keeble, director of public health told Suffolk County Council's local outbreak engagement board: "From our local data, we are picking up 14 or 20 cases but obviously these people who have gone to Latitude will be all over the country and that's part of the event research programme to try to piece together the impact of it.
"The thing I would say is you have got 40,000 people there, so if you look at the background rates of Covid in the population, which is about 1.4%, we would expect to see about 300 or 400 cases in that population over time, so it is quite possible the cases we are potentially hearing about are ones we would have seen in the population anyway."
How verification works
In order to be allowed into an event using the Certific app, people are required to prove their identity before recording themselves taking a Covid test.
If it comes back negative and reviewers are happy that the test has been done correctly, users are issued with an QR code that can be scanned at the entrance to the event.
- Get your Lateral Flow Test from the NHS.
- Download the app
- Enter the password that's emailed
- Fill in your info
- Upload a photo of your photo ID, such as passport of driving licence
- Complete video recorded test
- Wait for the result, which will come within four hours
- If you pass, you will receive a QR code, which you can present at the event
