Whether we have a nationalised rail service or what we have now, the important thing is efficiency. I think that is more likely with a nationalised service because the whole competition/shareholders needs/profit motive etc would be eliminated. And this chaotic mish mash that we have now would be streamlined.
I once spent many hours in a broken down train in the Severn Tunnel (with the resultant tailback of connections to countless other services) because the rail company would not use the nearest train to pull us out as it belonged to a different company and they would have had to pay - we waited hours until a train from the same company arrived. Crazy!
When a political leader lies on their CV - can you trust them?

