I had a burglary within a week of moving to a new house. I had
buildings insurance from the moment of ownership - but had only
arranged contents insurance over the phone - I hadn't actually posted
the cheque.

The insurance company (Standard Life) honoured the verbal contract made
over the phone and paid out without quibbling (and I was perfectly
clear with them that the cheque hadn't been posted at the time of the
burglary).