Can see some comments and suggestions in the press that the passengers would like this service to continue after the tunnel reopens
Sorry if I'm the bearer of bad tidings but Cardiff Central to London Paddington is some, a mere, 2 hours and 6 minutes by train.
Not that all of CWL's passengers live in central Cardiff, but then they don't all live in Rhoose or Barry either, but Cardiff Central to CWL, with a check-in that closes at STD -30, then an average block time of 67.5 minutes ... Well it's quicker, more reliable, more comfortable, more convenient and cheaper by train to a London terminus than it is by air.