After faffing around in my house, I exited to the conservatory, and thence to the garden.
Here I picked up the gloves and the secateurs. Then I went North.
Guardian appeared. I opened and closed the mailbox, then went back South. Then this happened. (Refer attachment)
How it is possible I don't know as I have both secateurs and gloves in my inventory. Maybe it was supposed to be triggered when I entered into that location the first time?