I disagree, Shuttl: the evidence in the UK is that attempted fraud is identified fairly quickly. See, for example,
https://www.bbc.co.uk/news/election-2019-50767154.
Moreover the Electoral Commission publish guidance on how to address the issue:
https://www.electoralcommission.org...and-detecting-electoral-fraud-in-Scotland.pdf
The attempted fraud consisted of;
"Allegations of voting fraud were being investigated at a number of locations in Scotland as counting began in the 2019 UK general election.
Renfrewshire Council said a possible case of personation had been reported to police in the Paisley and Renfrewshire North constituency.
At the Glasgow count, three cases are also being looked at while one is alleged in Stirling."
Five cases.
IME of policing elections, alleged voter fraud is mostly identified because someone turns up to vote to be told that they cannot vote, so the voter complains to the police. However, the vast majority of those are quickly solved by simple investigations that uncover the voter never registered to vote, or got a postal vote which they did not use and thought they could then just turn up and vote. Or, a mistake was made when someone turned up to vote, but the wrong name was scored out in the electoral role, so when that person arrived to vote, their name had a line through it. Supposed personation cases were often mistakes marking the electoral register as voters appeared.
I was even present when someone grabbed a ballot paper off another, marked it and put it in the ballot box! It was a husband and wife, the wife was wanted to get on with shopping, the husband was chatting, so she decided to just vote for him. We agreed, with the ballot station officers that no further action would be taken, since the wife had voted as her husband had said he would vote.