Unable to remove cap from top of Dorf tap

I need to change a washer in a leaking Dorf tap in our bathroom, but try as I might, I can't get the tap cap to budge.

It's a standard tap set like this one, and unlike the other taps in the house (which are also Dorf), the caps on this set seem impossible to remove via the usual methods ....



I broke a plastic tap cap spanner trying to budge it (ie. one of these spanners) ...



Normal hexagonal sockets won't fit the cap at all because the cap is octagonal, not hexagonal, so my next attempt on the weekend will involve vice grips. I've given it a generous squirt with WD-40.

Any other ideas?

some taps have a nut(needs a special tool)underneath the handle

Thanks mate. I had a look last night with a mirror and you're right - it looks like a ring with two holes is securing the tap head. Any idea where I can buy the special tool? I wonder if a pair of circlip pliers would work? eg ....

Any plumbers suppliers but if its extra tight you will find the spanner lugs straighten out or break off



Would probably be a whole lot stronger.

When you replace the nut add a smear of grease to make it easier next time