We bought my son's cello (new) last June, but seem to have a repeated problem with the A string breaking - the third one has gone tonight! Given that in six years prior to this we only had to replace one string this seems excessive. Can anyone suggest anything we can do to prevent this recurring? The strings in use are Jargar medium, as requested by his teacher.

Thanks for any suggestions

Have a Luthier (or the shop where you bought it if they are good) look at it. I think the most likely problem is a badly shaped groove on the nut (bit at the top of the fingerboard that it passes over before the peg) or a badly cut slot in the bridge that is pinching the string.

Best of luck