Armed police patrols, London, 1884?

[Khanada]

There is an item on the Wikipedia page, "1884 in the United Kingdom"
( http://tinyurl.com/6j6v22 ) that reads, "British Police officers go on armed patrol in London."

There's no date given for when this started; does anyone know if this actually went on? If so, do you know about when and/or how long such patrols lasted, or anything of the circumstances?

[PC2267]

I believe the armed patrols relate to officers specially trained in the use of sabres as apposed to armed with revolvers or rifles?