Nginx won’t start after upgrade from 16.04 to 18.04

I have just upgraded from 16.04 to 18.04 and nginx is not starting. One of the lines from journalctl -xe is:

nginx.service: Failed at step EXEC spawning /usr/sbin/nginx: No such file or directory

…and yes /usr/sbin/nginx doesn’t exist there.

This question seems the most relevant for my issue. However given that I’m going from 16.04 to 18.04 and the problem and resolution described therein are old and were temporary I’m wondering if this is some other problem.

All help gratefully received.

Of course if the solution is as described therein then I will carry that out but I’m reluctant to do so in case I cause more harm.