In article , Dave Plowman (News)
writes

In article ,
Mr X wrote:
Why would the police prosecute consenting sexual activity during working
hours anymore than other types of skiving off work?

Don't remain ignorant all your life - find out what the common-law
criminal offence of "Misconduct in a public office" entails and you will
have your answer.

http://www.cps.gov.uk/legal/section22/chapter_c.html

Seems they don't agree with you. And rightly so.

On the contrary, the last part of section b covers it:

(b) Wilfully neglects to perform his duty and/or wilfully misconducts
himself.
--
Mr X