What could be eating my strawberries?

Sorry if this is re-posted, only I don't know what happened to my post when I posted it. As it didn't show up. :( Never been that great with computers so I may have done something wrong lol.. well here goes again!

Ok I have no idea what is eating my strawberries this year, but all of the strawberries are being devoured as soon as they become ripe. See the image below.



I did have whitefly a few months back, but as soon as I spotted it treated it. And haven't seen any since, and have been checking it daily so I have ruled that out. I know it's not slugs or snails as I put some pellets around the urn and haven't found any dead ones at all. I've ruled out birds as I constructed a square covered in bird netting out of pipe and joints (see below) so it can't be that. And the plants are very healthy so I am now at a loss to work out what it is.



Any help that anyone could give would be so gratefully received, as I would like to have some strawberries and cream at some point this summer. :(

Kindest regards,
Oraya