The first Virgin Pendolino tilting train service from north Wales to London Euston had to be cancelled because of a problem with a diesel locomotive.
The trains can run at 125mph
The 0528 BST Monday train was unable to run from Holyhead, so passengers along the North Wales coast line had to take a diesel train to Chester.
They then took another to Crewe, to link up with the London service.
The 125mph Pendolino train will only tilt between Crewe and London.
It meant the passengers' arrival in London was an hour later than scheduled.
A Virgin Trains spokesman said: "Unfortunately there was a technical problem with the train at Holyhead which we could not fix in time and we had to cancel the service.
"Passengers used other services to get to Crewe."
It came on the day the Pendolino 125mph trains were introduced, aimed at cutting the journey of two hours 41 minutes between London and Manchester by 35 minutes.
Dafydd Huws of the Rail Passengers' Committee Wales said: "It's a bit unfortunate we had a problem in Holyhead this morning but there's an element of a gamble using an electric train, the Pendolino, and having to attach a diesel train to it
"Hopefully it's just teething problems and before long we'll hopefully see one of the world's most advanced trains serving north Wales."
The tilt allows trains to race through curves at higher speeds.
Work to allow the tilting was finished three months ago, with the trains built by Alstom near Birmingham.
Mr Huws said although the train would only tilt between Crewe and London, it would bring journey times down to north Wales.
"It will cut around half an hour off the journey time to London - it will bring Bangor as close to London in time terms as Swansea."
Prime Minister Tony Blair joined Virgin Trains head Sir Richard Branson at London's Euston Station last week to mark the entry of tilting trains into service.
Alex Aldridge, leader of Flintshire County Council, said he was sure the early problem was just a "minor glitch".
"We should celebrate what we're about to witness on this line and I'm pleased that the pressure from the likes of Flint town council and Flintshire county council has helped bring about this system."
Meanwhile, another Virgin tilting train from Glasgow was terminated at Carlisle after a wheel problem caused it to break down.
The new service includes extra trains and a ceremony was due to go ahead later to celebrate the arrival of the first direct weekday service from Euston in 40 years to the Llandudno town station.
It will be the first through weekday train from London to the resort since September 1964.
Virgin Trains already serves the Llandudno Junction station.