Actual knowledge

The UK's E-Commerce Regulations give some parameters to what "actual knowledge" is:

Notice for the purposes of actual knowledge

22. In determining whether a service provider has actual knowledge for the purposes of regulations 18(b)(v) and 19(a)(i), a court shall take into account all matters which appear to it in the particular circumstances to be relevant and, among other things, shall have regard to—

(a)whether a service provider has received a notice through a means of contact made available in accordance with regulation 6(1)(c), and

(b) the extent to which any notice includes—

(i) the full name and address of the sender of the notice;

(ii) details of the location of the information in question; and

(iii) details of the unlawful nature of the activity or information in question.