Science Editor Tom Clarke explains how the new track and trace app works
The NHS track and trace app is finally due to launch on Thursday after months of delay - but will it work?
The government abandoned its plans to set up its own Covid-19 tracing app in June to switch to technology used by Apple and Google, costing months of progress.
Many governments have tried with varying success to make apps that will use Bluetooth to tell users when they've been near someone who has Covid-19.
Scotland launched a similar app on September 10.
What does the app aim to do?
The app uses Bluetooth to keep an anonymous log of everyone you come into close contact with.
When they - or indeed yourself - present symptoms of Covid-19, you inform the app and it will then alert anyone that has been in close proximity.
The government has also said there will be QR codes to scan with the app in every restaurant or pub people visit to improve contact tracing.
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Will it help fight the virus?
Professor Pete Fussey, from the University of Essex and Research Director of the ESRC Human Rights, Big Data and Technology Project, said the app has several hurdles in its way before it is effective.
For it to be effective the app cannot exist in a vacuum, it will only be useful if there is an effective testing regime functioning nationwide.
In recent weeks the government has struggled to keep up with demand for tests, leading to delays and people being told to travel 100s of miles for one.
The QR codes which will inform the app when people visited different places will also need to be enforced by the owners of restaurants and pubs, which may prove unpopular.
Professor Fussey also said the key Bluetooth element may be "weak".
He said: "Bluetooth can connect through walls and other partitions.
"This means people in high density accommodation have increased likelihood of being misidentified.
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"These instances are also likely to occur in high density urban areas where health services are most likely to be under strain."
The app will also require large numbers of people to download it to work effectively.
Professor Fussey said low levels of adoption had been a problem for apps worldwide.
Will it protect our privacy?
The UK's previous centralised approach saw the contact matching being on a remote server managed by the NHS.
This was criticised by some as being less secure in a privacy sense, but the government argued it gave epidemiologists more access to data to better understand transmission patterns around the virus.
In contrast, the Apple/Google approach, which the new app uses carries out, the contact matching process on a user's smartphone itself.
Many other countries - including Germany, Italy, and Denmark - opted for a decentralised method developed by Apple and Google.
This makes it more secure and harder for any potential hackers to access and de-anonymise any data for nefarious means.
It also bars authorities from using the technology to collect any location data from users.
Professor Fussey said the government must detail what exactly the collected data will be used for and promise it won't be used for anything else.
He said: "The data protection impact assessment for the Isle of Wight trials demonstrated significant shortcomings and ambiguity."
He added: "In other countries there has also been the potential to reverse identify ‘anonymised’ data."
When will it launch for the rest of England and Wales?
The app will be available in England and Wales on September 24.