I have posted an article at The Conversation on this topic.
It's published under Creative Commons licence.
It is common for many employees to send, read and reply to work emails at all hours of the day and night, including weekends. This change in work culture developed in recent decades and has accelerated with the advent of smartphones. But is this a breach of employment law? The short answer is that “it depends” and we need some test cases to clarify the situation, not least in the UK.
Some workplaces have a culture of long working hours and it can be difficult for an individual employee to go against it. The contract may refer to a 40-hour week but the reality may be very different. Smartphones and other digital devices have contributed to a culture of “digital presenteeism”.
Staff may feel that, if they don’t keep up ....