I noticed on Facebook that someone whose name I recognised as a Gransnet poster is concerned about the security of postal votes. She is afraid that a party in which some MPs have cheated on their expense claims will somehow be able to suppress postal votes that go against them.
I have used postal votes for years, and I don't believe that there is anything particularly unsafe about the procedure, for several reasons.
One reason is that the administration of vote-counting, both those made in person and those by post, is not done by the party in power at the time, but by neutral Returning Officers. Another is that it is far more difficult to interfere in an election than to claim for expenses you are not entitled to!
A postal vote is not just an open letter to say "I, Joe Bloggs, want my vote to go to this candidate" It is more carefully designed than that, with the same safeguards as voting in person.
When you sign up to vote by post, you receive a postal vote pack a couple of weeks before an election, after a notification a week or so before that to say that it will arrive soon.
In the pack are:
A copy of the usual voting form, exactly as in a normal voting station, with the names and parties of candidates, and your unique number printed on it.
An envelope (A) to put it into, with a sheet of paper (the Postal Voting Statement) firmly attached to it, printed on this paper are instructions, your number and a place to sign that the number is identical with the number on your voting paper and to add your date of birth. You MUST NOT detach this, or your vote will be void.
Another envelope (B), pre-addressed to the returning officer, into which you put the sealed envelope A and post it.
The Returning Officer, who is independent of ALL political parties, organises Postal Vote Opening Sessions. The envelopes are counted and the number received is recorded. The outer envelope is opened and the details on the Voting Statement checked for accuracy. The inner envelope is still sealed, so it is not evident how a particular voter has voted.
The Statement is then torn off, and the unopened inner envelopes counted and put into a sealed box (just like the one at a polling station) Any that have had the statement torn off by mistake by the voter, or have any thing else wrong with them, are put to one side and counted separately.
When all the outer envelopes have been dealt with, the statements are removed and the inner ballot envelopes opened as a separate exercise, and treated exactly the same way as the votes that have been made in person and put into the sealed voting box at the polling station.
So the name of the voter and the name of the candidate they voted for are kept separate. The counting of actual votes is exactly the same as when the votes were cast at a polling station.
Candidates or their agents have a right to attend these Opening Sessions, but under strict protocol, to observe but not interfere. The rules, and more about the opening procedure, are set out at postal vote opening procedure, information for candidates Maintaining secrecy is paramount, and anyone trying to interfere and cheat is liable to an unlimited fine or six months in prison.
See also Who can attend a count for who can apply to be present (for general vote counting as well as postal votes, and members of the public as well as those with an official interest)