Complex sentence: When Woolley's loyalty to the minister is inconvenient to Sir Humphrey's plans, he readily makes oblique threats about Woolley's job security; however he is equally quick to defend Woolley from outsiders.
Split into simpler sentences: When Woolley's loyalty to the minister is inconvenient to Sir Humphrey's plans, he readily makes oblique threats about Woolley's job security. However, he is equally quick to defend Woolley from outsiders.