The execution of Wills in England and Wales is governed by the Wills Act 1837, passed when the idea of a video link was unimaginable outside the mind (perhaps) of Jules Verne, himself only 9 years old at the time.  

The Wills Act rules require a Will to be signed by the Testator (or someone authorised by them to do so) in the presence of two witnesses, both of whom are present at the time of signing.  "Presence" is currently accepted to be limited to physical presence.

During this period of social distancing and lockdown, several countries, including Scotland, have introduced legislation or guidance permitting Wills to be witnessed by video link.  In the case of England and Wales, the government has declined to do so, citing the need to balance the constraints of the COVID-19 situation against the important safeguards in the law to protect elderly and vulnerable people in particular against undue influence and fraud. 

It is possible that a lawyer may reach the conclusion, as in the case discussed in the link below, that a client is so ill and the circumstances are such that the only means of executing a Will is via video link.  In this situation, execution must be carried out, as it was here, with the clear understanding of the Testator both that the Will should be re-executed once it is possible for the Testator to do so, and unless and until this is done, that its validity may be challenged in court.  

Some commentators take the view that a court may make allowances for the unusual circumstances resulting from the current pandemic, or that it may construe "presence" to include virtual presence to take account of the technological developments that have taken place since 1837.  It is certainly a fascinating point from a legal perspective, but one that is unlikely to be resolved quickly.  

In the meantime, therefore, the best advice must be for Testators to execute their Wills in the traditional way; if they don't, they must be clear about the risks of witnessing by video link.