How can I fix my Blanco Mall 6300 tap?

I have a Blanco Mall 6300 tap, 4 years old, which is dripping. I would like to fix it myself but I can’t disassemble it to find out what is causing the leak as there is no obvious way to start the process. (I can get at the innards of the other taps in the house so I’m not totally clueless.)

It has a cross-head handle which resists any attempt to pull it away. The only obvious removable object is a grub screw on the handle. I removed this to reveal nothing useful. It seems to be there only to distinguish the closed from the open position when the water is turned off..

I would love to fix this myself but as you can see I am having no luck.

Can anyone help?