Clampdown 'prevented vote fraud' reports BBC

Ballot rigging by using forged postal votes may have been stopped because of a clampdown leading up to the general election.

Birmingham City Council's returning Officer Lin Homer said around 20,000 postal votes (approx 1/3 rd applied for) applied for were not cast on 5 May. (A similar proportion was announced in Blackburn).
“..the rigorous measures that the council and the police have taken against possible fraud may have deterred anyone on the list from using a vote which they obtained unlawfully.".... she said to the BBC.

It is evident that the general public brou ha ha will have frightened off any large scale attempts at fraud as returning officers took every possible precaution to stop any form of vote rigging. There are many people who see the massive non use of postal votes as evidence of the preparations for wide scale fraud.