Gross apologies paulm. I'm much surprised to find nerveless can be both bold, brave etc and its own antonym. See below from the online thesaurus.
Main Entry: nerveless
Part of Speech: adjective
Definition: scared to death
Synonyms: afraid, cowardly, debilitated, enervated, fearful, feeble, nervous, petrified, spineless, timid, weak, yellow-bellied