That was the nastyness of the earlier announced zero day. All the attacker needed was to have the file on your system when Microsoft's malware scanner ran.
It really should be the case that IT infrastructure is resistant to these problems.
http://www.suspension-nhs.org/Resources/Safety%20-%20IDT%20(...
In that tree (which is about harm to patients) the path to "consider suspension" is "were the actions as intended?" and "were adverse consequences intended?" (Did you harm the patient, did you mean to harm the patient?)
You get referral to the regulatory body (which may lead to suspension or dismissal) if someone took an unacceptable risk and there are no mitigating circumstances.
The point of NHS.Net email is that it is secure. A staff member should be able to open email without causing havoc.
There's a lot of focus on human factors in the NHS, and that tends to avoid things like blame.