School children are asking teachers how to strangle a partner during sex safely, a charity says, while official figures show an alarming rise in the crime related to domestic abuse cases. It comes as a woman whose former partner almost strangled her to death in a rage has advised anyone in an abusive relationship to seek help and leave. Sky's Ashna Hurynag spoke to Kerry Allan who was a victim of domestic abuse. Warning: This videos contains references to strangulation, domestic abuse and