Phil L wrote:

A 45 degree bevel on a step? - are you sure it's not just a kerbstone laid
flat on it's back?
Either way, you can't 'chamfer' concrete in this way, you are right to
assume that it will crack up, the only way to stop this is to give it more
depth, IE cut out a straight line with a grinder and chisel off an inch or
two in depth, treat with neat PVA prior to concreting and scrape some slop
into it.

Yes a chamfer would have been a better word; when I cast the steps some
25 years ago I obviously put a chamfer on the leading edges so that
they wouldn't chip. OK I'll now have to cut it out !! Thanks for the
advise.

Rob