Most people don’t vote

About 70% of the electorate vote nowadays, it has varied higher or lower but never been as low as 50% of eligible voters to even say “half of eligible people don’t vote” let alone “most”

https://researchbriefings.files.parliament.uk/documents/CBP-8060/CBP-8060.pdf

So assuming you have say 20 old people on your fictional bus, even assuming that all of your voter info is correct and everyone is on the register, the chances of all of them being able to cast a second vote without any of them being caught are billions to one.

The idea that millions of people will risk a significant chance of a lengthy prison sentence for their individually tiny extra votes is absurd when any actual attack on election integrity would not happen at the point of “turning up at the polling station and hoping for the best.”

Even if one in a million voters did try and get away with this - which again is a hugely inflated number from anything we get an indication of - if to do so you stop tens of thousands of people from being able to vote at all that still makes the election less democratic overall.

Why would you need a passport if you aren’t leaving the country?

It’s a piece of paper you buy every ten years if you want to travel across national borders, it’s not like some intrinsic part of your being.

At the point that the new voter ID legislation was introduced, about 8% of the electorate - ~3.5m people - did not have a passport or a driving licence.