Is this declining performance really a recent thing?
I've been making long distance trips on the network since 2013 and 50% of the time, I get delayed by at least 30 minutes on one leg, often a lot more. Most recently was last Tuesday on
this train I took to Cardiff.
There was failed aircon in 2 Mk3s with a third giving up half way through. There was no counter service or water on board. We were delayed at Reading to procure water for those feeling unwell, then an inexplicable increase in delay as the journey progressed. At Swindon we picked up the passengers of the
preceeding Swansea service which had broken down. They had been waiting there for 90 minutes.
A few weeks ago I got delayed by 45 minutes between Swindon and Bristol TM due to signalling problems.
Random cancellations due to crewing issues or signalling problems, usually in the Bristol Parkway area have been the most common causes of the delays I've experienced. People seem to get hit by trains east of Slough 2 or 3 times a week - that alone puts me off ever wanting to commute on that line. Other high speed lines I commuted on like EMT and HS1 were very reliable. Using GW is a bit of a lottery and it's irritating as those delays cut into your time which you never get back.
In my view it has been an unreliable part of the railway for at least a few years.