Not enough. They do a weekend course every six months in unarmed arrest and restraint techniques. I’ve had over a decade of experience martial arts training (inclusing Ju Jitsu and Krav Maga) and even with that I am not confident that I could take on a knife wielding attacker and not end up getting stabbed or slashed 100% of the time. The average bobby does a hell of a lot less training than I’ve done and they’d be damn lucky if they managed to pull off a successful counter attack and disarm. They do in fairness have a baton and cs spray though.
True, in a knife fight you’re probably going to get cut. There was an infamous case in Tucson some years ago where a U.S. Navy SEAL was stabbed to death in a restaurant parking lot following some type of stupid encounter. Anyone is vulnerable, no matter their training.