Despite all the subsequent social changes, this tradition still persists. Even now, polls of serving police officers show a clear majority against routine arming, although that majority is smaller than it once was. And 'unarmed' is a bit misleading - there have always been armed officers, but the key thing is that the ordinary copper on the street isn't routinely armed. The view is that it's better that guns should be in the hands of officers intensively trained for the purpose, rather than every ordinary officer who has no special interest or training, only does the minimum range time necessary, will rarely if ever need his gun, but may use it inappropriately when he does.
Whatever the rights and wrongs of this (clearly there are sound arguments on both sides) the fact is that deaths and serious injuries to UK police officers while on duty are rare. Since 1945 only 250 have been fatally shot.
Thanks for that explanation! Sounds like it was a nod to the tradition of liberty in the UK compared to the continent.