Two of Virgin's new high-speed tilting trains have broken down, marring the launch of the passenger service.
The tilting technology promises a faster ride
The Virgin Pendolino should cut journey times between London and Glasgow by about half an hour.
But the flagship "Royal Scot" terminated at Carlisle after a wheel problem caused it to break down.
And the 0528 BST Holyhead to London train failed to start, causing passengers to travel to Crewe to pick up the London service.
The £7.6bn project, which has caused disruption to millions of passengers, is due for completion by 2008/2009.
Passengers on the 0949 BST service from Glasgow were transferred to another train in Carlisle after it limped into the station an hour late.
It was travelling at 50mph instead of 110mph.
The passengers are expected to reach London two hours later than planned.
Virgin Trains said the problems were very disappointing but only two of 78 tilting services had experienced difficulties and the wheel problem was extremely unusual.
Following the disruption, a Virgin spokesman told BBC News Online: "We apologise to those passengers who were on those two trains that were affected and everything is being done to ensure that they complete their journeys as quickly as possible.
"If they are significantly delayed, compensation will be paid as normal".
He added that the cause of the problems in Holyhead, north Wales, was unknown and was being investigated.
FACTS ABOUT TILTING TRAINS
British Rail tried and failed to launch tilting trains in the 1980s
The first Virgin Pendolino train was launched in July 2002
The trains were originally forced to run in non-tilt mode
Features on the trains include video and audio entertainment
Virgin Trains claim journey times will soon be cut by 25%
The trains will only tilt and reach their top speed of 125mph south of Crewe because the line between there and Glasgow still needs upgrading.
From Monday, the new timetable between London and Manchester will be a journey of just over two hours - a reduction of 35 minutes - while 20 minutes will be taken off the trip from London to Birmingham.
The upgrade between London Euston and Manchester started in May 2003 and involved about 9,000 people working a total of 24 million hours.
Around 460 points have been installed on the completed section as well as 600 miles of overhead wiring and more than 1.1 million tonnes of ballast.
The first stretch of track that allowed for 125mph trains running "in tilt" was completed in December last year between Rugby and Atherstone in Warwickshire.
New platforms have been built at Birmingham New Street station and Wolverhampton to help increase capacity. Platform extensions have also been completed south of Northampton.
The West Coast Main Line was built in the 1830s and has developed into the UK's busiest mixed-use rail route and now serves about 75 million people each year.
It handles over 2,000 trains each day, including 43% of the country's freight traffic.