While human contact tracing is well under way, the app effort has struggled through delays and concerns about privacy.

Now, the Government has done a U-turn on the technical approach it is taking under the bonnet of the app, turning to tech giants Apple and Google as other countries have done.

– 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.

However, there has been debate about whether the UK’s centralised approach, meaning a computer will receive data when the individual chooses to share it, is the right one.

Many other countries have opted for a decentralised method developed by Apple and Google.

So, how does the Apple/Google decentralised system work?

In the UK’s previous centralised approach, the contact matching is done on a remote server managed by the NHS.

This has been 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 carries out the contact matching process on a user’s smartphone itself, making it more secure and harder for any potential hackers to access and de-anonymise any data for nefarious means.

Their system also bars authorities from using the technology to collect any location data from users.

Is anyone else already using the decentralised approach?

Yes, a number of other countries have already sought to access the Apple/Google system for their own contact-tracing apps, including the Republic of Ireland, Germany and Italy.

Authorities in Denmark, Switzerland and Austria are also using apps based on a decentralised model.

It has been noted that another advantage of the UK adopting a decentralised approach is that it would make it easier to make the NHS app compatible with apps in these other countries as they would be based on the same system.

– What were the privacy issues surrounding the centralised way?

One concern was whether the app could be abused to track people’s movements – something the Government said would not be possible, and that data will only be received once the person decides to send it manually.

However, that was not enough to stop privacy issues from being raised, with Amnesty International UK among the bodies to speak up on the matter.

Joint Committee on Human Rights chairwoman Harriet Harman MP called for new laws to protect the privacy of personal information gathered by the coronavirus contact-tracing app.

– Why the change of heart?

The Department for Health and Social Care said during tests on the Isle of Wight “technical challenges” were identified.

This included the reliability of detecting contacts on specific operating systems – an issue they said “cannot be resolved in isolation with the app in its current form”.

Officials said the app was highly inaccurate when used on iPhones, only identifying around 4% of contacts.

However, they added “there is still more work to do on the Google/Apple solution which does not currently estimate distance in the way required”.

The Government said its new app design will bring together the work on its own development with the Google/Apple solution.

– Will a contact tracing app solve everything?

No – as ministers and leaders on the project have been keen to point out, it’s no “silver bullet”.

But it can help alongside traditional human contact tracing methods.

– When will it launch for the rest of England?

Health Secretary Matt Hancock originally said the app would be rolled out across England by mid-May – that time has since passed.

Number 10 then said it hoped to roll it out more widely “in the coming weeks”.

But on Wednesday, Lord Bethell, the minister responsible for the smartphone app, told MPs that the much-anticipated technology may not be ready until the winter.