I've been in touch with my ex to tell her that her official polling card had arrived. She was a little surprised because she has had one for her new address. Does this mean she could technically vote twice? If she can, then something is wrong with the system.
There is always the possibility of being on the electoral register twice e.g. students, who can register for both home and term time addresses. In a parliamentary election you can only legally vote once, however. The onus is on you to keep to the rules.
The rules are different in local government elections. The student in the above example can vote in both home and term time local election (assuming a fast enough car!) but not if both addresses are in the same Local Govt area.
Thanks dundurn, her new address is in the same local govt area. I presume that she will be signed in via a computer link then? Otherwise how else would they know?