How to remove a Stuck tap cover

[Debs]

I am trying to remove the round cover on a tap to get to the tightening screw. It used to screw off but is stuck fast. Any ideas how to loosen this. Many thanks

 

[rpm]

Pour boiling water over then try wearing rubber gloves (the kind with the little bobbles give a better grip).

 

[Ted808]

stanley knife...carefully