How do I change this tap washer?

[justagoose]

I've changed many a tap washer before but I can't work out how on earth to get at the one in this tap. I thought the cap might lift off to unscrew but it seems to be stuck solid, am I missing something?

Thanks in advance!

 

[Wayners]

Put masking tape on cap. Apply with bumps and ridges so you can get a grip and turn.
That's how I would think it would come off.
Not saying I'm correct

 

[justagoose]

Thanks I'll give it a try