XF 2.0 Show content on 1st post only


Previously Cylent1
I am tring to show content in 1st post in a thread only.
I am trying this but does not work: <xf:if is="{$post.post_id} == '1'">.
Any ides?

I jumped the gun and posted this, It does work.
Can I just ask where you are posting this - would love to turn around and have this on my site in order to encourage people to register / login to read it all.