The beleaguered NHS Covid-19 contact tracing app will finally launch in England and Wales on September 24, the Department of Health has confirmed.
Officials have repeatedly delayed the rollout of the smartphone software since it was first expected in May but trials on the Isle of Wight failed.
The app will add to the NHS Test & Trace service which aims to track down people who have been close to those infected with the coronavirus.
It will use Bluetooth to keep an anonymous log of everyone each user has been close to, and alert them if one of them tests positive for Covid-19.
Health Secretary Matt Hancock said today: 'We need to use every tool at our disposal to control the spread of the virus including cutting-edge technology.
'The launch of the app later this month across England and Wales is a defining moment and will aid our ability to contain the virus at a critical time.'
The announcement comes after Scotland's First Minister, Nicola Sturgeon, yesterday launched the 'Protect Scotland' app north of the border.
Officials abandoned the NHS's attempt at making its own app in June when they realised it didn't work on iPhones (Pictured: The app in development stages)
England's beleaguered app, of which the first version had to be scrapped in June after a string of failures, has now been recreated using technology made by Google and Apple - bringing it in line with apps made in Scotland and Northern Ireland.
Bluetooth technology will keep a record of which phones spend 15 minutes within 2metres (6'7') of one another and then alert people if they have been near someone who later tests positive for Covid-19.
Users will also have an 'isolation companion' which has countdown timer if someone has to self-isolate, and will be able to 'check in' to places such as pubs and restaurants using QR codes.
They will also be shown what the risk level is in their local area based on the first half of their postcode, with places being categorised as low, medium or high risk.
How does contact logging work?
While the app is running Bluetooth technology will keep a record of which phones spend 15 minutes within 2metres (6'7") of one another and then alert people if they have been near someone who later tests positive for Covid-19.
People's phones are only recognised by the system if they are running the app themselves - it cannot detect others.
The contacts it keeps track of are all anonymous and phones exchange digital 'tokens' with every app-using phone within Bluetooth range.
If one person develops symptoms of the coronavirus or tests positive, they will be able to enter this information into the app.
The phone will then send out a notification to all the devices they have exchanged tokens with during the infection window, to make people aware they may have been exposed to COVID-19.
Each phone keeps an individual log of the Bluetooth profiles someone has come close to. These will then be linked anonymously to people's NHS apps and alerts can be pushed through that even after the person is out of bluetooth range.
People can delete their data from this app at any time.
Will the app tell me what to do?
The app can only react to data that people put into it, and it will only ever offer guidance. If a user reports that they have symptoms of coronavirus - a new continuous cough, a fever, or a changed sense of smell or taste, they will be urged to self-isolate for 10 days from the start of the symptoms and to get tested.
If they test positive for Covid-19 at any time, they should report this to the app. The app then sends out an anonymous alert to everyone with whom that person has been within 2m (6'7") of for 15 minutes or more since they started feeling ill.
That person may then be asked to self-isolate or to get tested if they feel unwell.
The app will rely totally on members of the public co-operating, volunteering to let it track their connections and following the instructions it gives them on getting tested and self-isolating.
The app is far from perfect, though, and the Department of Health has admitted that around half of people who are warned they have been near an infected person will actually not have been within the 2m for 15 minutes danger window.
And three out of 10 people who were put at risk - 31 per cent - won't receive a notification at all. In trials it had a 69 per cent accuracy rate at detecting people who had been at risk, and it was 55 per cent accurate at detecting people who had not.
The newest version of the app is being launched after the first attempt was abandoned in June because it did not work on Android smartphones.
The NHS's app — which was originally promised for mid-May and the NHS spent months developing — was unable to spot 25 per cent of nearby Android users and a staggering 96 per cent of iPhones in the Isle of Wight trial.
This was because the Bluetooth system developed by the NHS effectively went into 'sleep mode' when the phone screens were locked and developers couldn't fix the glitch.
Different Bluetooth technology made by the phone manufacturers Apple and Google themselves has turned out to be significantly better at detecting other phones.
Officials said the app software now reliably detects 99.3 per cent of nearby app users, regardless of what type of phone they have.
And it will use, on average, two to three per cent of a phone's battery life each day, officials say.
Another major difference between the two is that Apple and Google's technology stores the anonymously log of someone's contacts entirely in the phone - it is never shared with anyone else and can be deleted at any time - whereas the NHS's worked on a system which meant it had to be sent to a centralised database.
Officials have changed this to squash concerns about privacy, now insisting the app 'tracks the virus, not people'.