Having had to fire someone who had been at a company for more than two years, I can say it was anything but a simple procedure: it involved a performance improvement plan which lasted interminably (and actually sapped a really surprisingly large amount of my own time...) and it became an awful lot more complicated when it turned out the guy was on anti-depressants. In the end, HR suggested I take the guy to the pub for lunch and they told me a series of things I could say to encourage him to quit but which couldn't possibly be construed as constructive dismissal; thankfully over lunch he told me he'd got another job offer, and I walked him out of the office the following day with a great sense of relief.