In article
,
says...

As so often happens (apologies) having posted the question I almost
immediately found the answer:

K1 1.34 (c): If the stairs are 1000mm or wider: provide a handrail on both
sides.

https://assets.publishing.service.go..._AD_K_2013.pdf

You also need to take into account who will be using them.

For example, I walk with a stck in my right hand so, if I'm
forced to use stairs, it is important to have a handrail on
the left in BOTH directions, irrespective of the width of the
stairs.

--

Terry