Both exist. Assurance pays out WHEN something happens and insurance pays out IF something happens.
You need an insurable interest in the life being covered in order to take put a policy. I don't think (not 100% sure though) you need their knowledge or consent - but you might have difficulty answering the medical questions without it and still more if a doctor's report were needed after death - you'd have no right to one so your claim wouldn't be paid..
It's Assurance, there is no such thing as insurance, however to appeal to the LCD often firms use the term "life Insurance" but it is wrong. As above you need an insurable interest. In the early days of life assurance it was possible to assure people without their knowledged but that was stopped when people started assuring soliers going to war etc.
when I worked in insurance, it was Life Assurance (being the certainty) but buildings Insurance (in case it happened). You can only take out a policy if you have an insurable interest in the person or thing being covered.
I you want to take out a policy on your partner it would probably be best to take a joint policy which pays out on first death then you will both benefit whicher dies first.
Both will have to agree, fill in medical questionnaire and sign