Scratch the bark on the main stem, and see if the wood is brown (dead) or green (still alive). I thought my pink Ceanothus was dead, but it has small shoots appearing, so it may well be worth hanging on for a while.

Hello Lyndyburg! Welcome to Goy! The same thing happened to me with two standard Buxus, the Buxus hedge beside them was absolutely fine! However, after advice from another Goy member-Tugbrethil, I watered them with dilute feed to stimulate growth and waited... and just today they have started to leaf up again! I'll prune them lightly back into shape when they have recovered a bit more. So, just as Spritz says where there's green under the bark, there's hope!

Thanks very much Spritz and Libet - I will do as you suggest. Here's hoping ...