In a large bowl, whisk the heavy cream for a few minutes until you've got stiff peaks.

Carefully fold in the condensed milk then pour the mixture into a large container suitable for freezing.

Add the strawberries, sugar and water into a blender. Process for 1 minute - scraping down the sides of the blender as necessary - until the strawberries have totally broken down.

Pour the strawberry mixture in an even layer on top of the ice cream in the container. Use a spoon or knife to draw swirled patterns through the strawberry layer into the ice cream, so the two layers get swirled together.

Leave in the freezer for at least 8 hours to set.