In the event of an internet outage, wall box chargers are legally required to default on. In practice most chargers interpret this as taking the full 7kw - whether this is a bug or misreading of the intent of the law doesn't really matter from the perspective of the grid.

Large ISP outages that affect millions of people are not uncommon on a decade by decade basis, and I suspect an uncomfortable number of UK EV chargers are in some way linked to eu-west-2.

[1] https://www.legislation.gov.uk/uksi/2021/1467/regulation/7/m...