There was a very helpful thread on garden steps some months back: thanks to
everyone who chipped in.

One thing which didn't crop up then was this: I've looked at the online
regs but can't find this specific information.

I'm about to install sets of steps from my two patio doors and back door
down to the existing ground level; the drop is almost exactly 600mm. Is it
necessary to have handrails and vertical bannisters on both sides of each
set of steps, or is it sufficient to put them on one side only?

Thanks.