Don't know if these links are helpful to any one - always good to raise awareness:
https://www.womensaid.org.uk/information-support/what-is-domestic-abuse/recognising-domestic-abuse/
http://www.refuge.org.uk/about-domestic-violence/barriers-to-leaving/
Often men like IS behave start the relationship being kind, gentle, emotionally available etc - this is what makes the victim fall for the perp. The behaviour then changes and the behaviour becomes abusive. But outside of the home and to onlookers generally the perp is seen as a charming kind, generous person - this makes the victim think they are the problem.
The freedom programme is very good at understanding how these men/women think and how the cycle works/how it can be broken.
Exactly
And in the insights we have into Helen's state in her final months - I think we can see that playing out in her uncertainty and confusion about what was happening to her.
But now we know he was driving all of this
So in a way I can easily believe the killing was not planned (though it may have been part of his fantasy).
I suspect he instead went too far - we see that all the time with abusers.