"Another option albeit slightly more expensive is a live trap. It will
allow you to check that what you really have is a rat, if not you can
let it go." and do what with it if it is a rat? Most people don't have
a gun handy nor are they able to safely get the rat out and bash it on
the head with a brick. Drowing is cruel and illegal.
Use poison, use it safely and it is effective. Most modern poisons
have no secondary effects. Get the council out to do it as they know
what they are doing. Buy a rat zapper which electrocutes instantly and
mostly, stop throwing food on the ground as it will attract rats. Get a
bird table with a lip to stop seed blowing off it.