Implementation of a Vaccine Passport in the UK has many legal and technical challenges, which I personally believe are insurmountable.

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If order for such a scheme to be viable, it has to achieve at least two aims:

* Attest to your identity
* Attest to your vaccine status

Let's take each of these in turn.

Attesting to your identity , in any meaningful way, will require a photograph. In the government mock-ups of a VP they use a person's passport photograph for this purpose.

Around a quarter of all people in the UK have no UK passport. Many hold foreign passports but these...

...cannot be used, as HMG has no access to that image asset. Also a great many people have no passport at all. This is especially true of the elderly and children.

Back filling with Driving Licenses actually leads to worse figures, not better.

In any case, using a passport photograph for this purpose will require either re-consent or an interdepartmental data sharing agreement that is subject to the legislature.

This sort of agreement had to be put into place in order to achieve EU settlement scheme automatic...

... status verification between the Home Office, HMRC and DWP. Such agreements take a long time to put in place and are subject to legal challenges.

Having said that, HMG did break ICO rules by sharing people's vulnerable medical status with some retailers. This is not legal..

..but the ICO turned a blind eye, due to the "emergency" situation at the time.

Getting photographs for the missing 25% of people will be a huge endeavour. It requires at least two copies, certification of the image by a responsible person and human checking in the HO.

Another route to acheiving identity verification is to use the NHS app. But there are even more people who do not have this app and many who have no device on to which to install it. This is not the same as the track-n-trace app which has no robust identity management at all.

In order to use the NHS Patient Access app for the first time, you need to present paper evidence of your identity in-person at your GP surgery. Millions of people doing this all at the same time will not work.

So what about your vaccine status? Well this too would need a data sharing agreement. There is no precedence for a such a contract between the DoH and the rest of government.

Even if there were, NHS IT is in an appalling state and effort required to pull such data will be...

...immense. Especially given the data is changing all the time. The latency on the EU SS data pipes was of the order of weeks. People want wait for weeks to get a seat in a restaurant.

In any case, such an app would need to be passive at the point of use. That is, not be required to make a network access at that point it is shown. The alternative would be for HMG to host a suite of live, low latency servers which there is no evidence they can achieve.

The track-n-trace app is passive in this way. The scanning of the QR code makes no network access and simple store the record locally on the phone.

Passive apps are trivial to reproduce in HTML / CSS.

All-in-all, I don't think that a robust Vaccine Passport app is possible. What we will get, at most, is a sort of self certification scheme based on the honest responses of the user + a huge fine if you are caught lying.

No one will take this seriously.