The Pensions Regulator (them again!) answers this pretty thoroughly (see below).
I would add that this is applicable to one person limited companies even if you pay yourself a salary (which in most cases is likely).
……..
Automatic enrolment duties don’t apply when a company or individual are not considered an employer. You won’t have any duties if you meet one of the following criteria:
- you’re a sole director company, with no other staff
- your company has a number of directors, none of whom has an employment contract
- your company has a number of directors, only one of whom has an employment contract
- your company has ceased trading
- your company has gone into liquidation
- your company has been dissolved
Automatic enrolment will apply if more than one director has a contract of employment.