Probably illegal, depending on the exact circumstances.
"a photograph or film is disclosed if it, or any data or other thing which is capable of being converted into it, is given, shown or made available to a person other than B."
From a quick reading, you can't just have it, you have to have consent to show it or a really solid reason why it had to be shown (such as in relation to another investigation, like this was the only photo that was proof)
So no, showing off someone's private pics you took if they did not consent that you could show them would be considered illegal under this. Basically the law codifies the transaction of intimate pictures
Relevent section: (1)A person (“A”) commits an offence if—
(a)A discloses, or threatens to disclose, a photograph or film which shows, or appears to show, another person (“B”) in an intimate situation,
(b)by doing so, A intends to cause B fear, alarm or distress or A is reckless as to whether B will be caused fear, alarm or distress, and
(c)the photograph or film has not previously been disclosed to the public at large, or any section of the public, by B or with B’s consent.
(2)For the purposes of this section, a photograph or film is disclosed if it, or any data or other thing which is capable of being converted into it, is given, shown or made available to a person other than B.
(3)In proceedings for an offence under subsection (1), A has a defence if any of the following facts is established—
(a)B consented to the photograph or film being disclosed,
(b)A reasonably believed that B consented to the photograph or film being disclosed,
(c)A reasonably believed that disclosure of the photograph or film was necessary for the purposes of the prevention, detection, investigation or prosecution of crime, or
(d)A reasonably believed that disclosure of the photograph or film was in the public interest.
(4)For the purposes of subsection (3), consent to the photograph or film being disclosed may be—
(a)consent which is specific to the particular disclosure or (as the case may be) the particular threatened disclosure, or
(b)consent to disclosure generally where that consent covers the particular disclosure or (as the case may be) the particular threatened disclosure.
The law relates to "a photograph or film which shows, or appears to show, another person (“B”) in an intimate situation,"
which is further defined:
"a person is in an “intimate situation” if—
(a)the person is engaging or participating in, or present during, an act which—
(i)a reasonable person would consider to be a sexual act, and
(ii)is not of a kind ordinarily done in public, or
(b)the person’s genitals, buttocks or breasts are exposed or covered only with underwear."
How about this. Would you be comfortable with someone who had an intimate/sexual photo of you sharing it around?
Don't be shitty to other people. Why is this hard?
edit: just noticed there is an intent requirement in the law as well.