Secrecy in voting

SIR – I have just completed my postal vote. The sheet of instructions told me to check that the reference number on my voting slip and the number on my mail return slip coincided. I then had to sign and fill in my date of birth on the return slip before posting it.

Since there is now a ready crossreference between the two, what has happened to the secrecy of my vote? Joe Gibson

Redhill, Surrey