Many flat-buyers (and, increasingly, those purchasing new-build properties) find they are a leaseholder rather than a freeholder.
This means as a leaseholder they only have the right to live in the property – they don't actually own the building or land it's built on. That belongs to a separate landlord or property management company.
In this case, it's almost always a landlord's responsibility to insure the buildings part of your home – its structure, cost of rebuild etc in the event of a disaster – but NOT your contents (do check, though).
If you're a leaseholder, don't fall into the trap of thinking your landlord covers your contents insurance as well; you WILL need to buy your own policy.