(1)A person aged 18 or over (A) commits an offence if—
(a)he intentionally engages in an activity,
(b)the activity is sexual,
(c)for the purpose of obtaining sexual gratification, he engages in it—
(i)when another person (B) is present or is in a place from which A can be observed, and
(ii)knowing or believing that B is aware, or intending that B should be aware, that he is engaging in it, and
(d)either—
(i)B is under 16 and A does not reasonably believe that B is 16 or over, or
(ii)B is under 13.
(2)A person guilty of an offence under this section is liable—
(a)on summary conviction, to imprisonment for a term not exceeding 6 months or a fine not exceeding the statutory maximum or both;
(b)on conviction on indictment, to imprisonment for a term not exceeding 10 years.
20.Section 11 makes it an offence for a person (A) aged 18 or over intentionally to engage in sexual activity (as defined in section 78), in order to gain sexual gratification, when a child aged under 16 is present or in a place from which A can be observed. Where the child is aged 13 or over but under 16, the prosecution must prove that A did not reasonably believe that he was 16 or over. The offence is committed if A knows or believes that the child is aware that he is engaging in the activity or intends that the child should be aware of this. This offence would cover, for example, A masturbating himself in front of a child, or A masturbating himself in the presence of the child to whom he is describing what he is doing, perhaps because the child is covering his face. It would also cover the situation where A performs a sexual act in a place where he knows that he can be seen by a child, for example via a webcam.