Removing boot insert from Berlina garnish lights?

So I bought a Berlina garnish today from a wreckers shop. I noticed there was a decent buildup of mud in the nooks and crannies of the garnish, specifically the gap between the lights and the boot insert. So i was wondering, how do you separate the white insert from the garnish lights, just so i can clean it up and get it looking noice.
Cheers.