Changing a tap washer!!

[2Btoo]

I have a dripping tap. Two of them actually.

I know how to change the washers on a tap but don't know how to get this type of tap apart. They are a common (slightly old) model and look like this;





The tap body is clearly in two pieces with a join in the middle and I am guessing I need to take the top bit off but don't know how. Does it twist off? (There are no flats on it to put a spanner on). Does it need to be tapped off with a hammer and drift?

All help welcome, thanks.

[2Btoo]

Kenny, thanks but I don't think that the tap handle (the cross-shaped bit) needs to come off although I could be wrong.

Fatboy, thanks also. The problem is that the top bit of the tap body won't move, even with a pair of stilsons attached across it and turned firmly (although I did scuff the chrome slightly, which is a bit annoying.) Am I doing the right thing? Is it just that it's been there for a long time and some PlusGas (or similar) will be needed to get it moving?

Thanks.