English voting is kept reliable and secure by the physical security over the ballot papers - so simple a child can understand and be sure of the system.
The principle is that a single paper is issued to a voter, and is then monitored from voting booth to the count. It is either in sight, or in a box with a seal -approved by the polling staff and candidates (or their agents). So a candidate can be as confident as humanly possible that there has been no tampering to rig the result.
Postal votes are a different matter, as they enter the polling system by post - there can be no certainty as to who they were completed by, and no assurance that a ballot is even received by the polling staff - it needs complete reform.
I believe it should be a criminal offence with a significant minimum term (say 5 years) to mark or tamper with another voters ballot paper in anyway.
Any alternative voting system, must retain this simple, visible, security - electronic/mechanical voting or counting should only ever be considered if it can meet this same standard. A machine for counting ballots may be possible if it visibly cannot introduce, change or discard ballot papers, and its results can (could) be manually verified.
A voter must be confident that their vote has been accurately counted, and that only (and all) valid votes cast by other legitimate voters are included in the result.