I'm thinking of buying some bitcoins. Before I do I want to be sure that I can backup and restore my wallet - Bitcoin Core. This seemed to go ok, the bitcoin loaded into the new wallet which was on a different computer from the original. The original bitcoin wallet still shows the old balance.
I'm sure it's unlikely, but what if someone stole my computer and I then restored my bitcoin to a new wallet - would the thief be able to spend from the original wallet after I'd done the restore?