On What Evidence?

It's a punishable (I dont know about sackable) offence even if the sex was consentual. I understand what you're saying about inadmissable evidence that means the court case didn't hold against him, but if the entire MET knew he was guilty then his position would be untennable

My understanding is officers usually aren't sacked for sex on duty/on police property/etc. However, I won't pretend it's an area of expertise for me.

Untennable-position wise, you make a good point.