There is a lot of confusion about BS3621. It isn’t always easy to know if your locks are compliant with home insurance policies.
BS3621 is a British Standard for door locks, this means you can be confident any lock marked with the standard is a good lock with a good level of security. For a lock to be certified with BS3621 it must meet all the security requirements.
Insurance companies don’t want your house broken into because then they have to pay out. This is why they want your locks to comply with BS3621, it is much less likely a burglar is going to make it into your house if you have good locks. Make sure to read your insurance policy carefully so you know what type of locks you are required to have.