Thousands of train passengers suffered delays on Britain's busiest rail line on Saturday, as a massive upgrade of the track began.

The �6.3bn upgrading of the West Coast Mainline from London to Glasgow is scheduled to go on every weekend until December and will add an hour to journeys.

It will eventually mean that Virgin's 125mph Pendolino trains can run at full speed.

Railtrack says the disruption is unavoidable as it struggles to catch up with the renovation of the line, which is months overdue and way over budget.

A spokesman for Virgin Trains said: "The work being done is equivalent to closing all six lanes of the M1 and resurfacing the whole lot in one go and we are having to do it over a 26-mile stretch."

Disabled passengers

The line between Hemel Hempstead and Milton Keynes will shut down each weekend from now until 8 December, affecting passengers travelling with Virgin Trains and Silverlink.

This weekend the train operators have arranged for 150 coaches to meet every train, transferring passengers from station to station.

We believe we have done all of the planning and we're now going to deliver

John Brooks - Silverlink

Some will be express services while others will stop at all stations in between.

Disabled passengers will have to contact train operators in advance to arrange for specially-adapted transport.

John Brooks, Silverlink county route director, said it was trying to minimise disruption to passengers.

He said: "It's train-coach-train if you're going into London but we've got an additional 200-300 staff around the system helping out. We've got an additional 150 buses, with 80 further ones on stand-by.

"We have engineering staff on stand-by if things go wrong so we believe we have done all of the planning and we're now going to deliver over the next 18 weekends."

Passenger frustration

A spokeswoman for Railtrack said it had tried to limit the inconvenience caused to passengers, "coupled with the aim to complete the work as quickly, and as practically, as possible".

Frustrated passengers described the country's trains to a "Third World" operation.

Chris Marchington of Surrey, travelled to Manchester's Piccadilly station to see a Manchester United match.

Coaches are being used to complete journeys

He and his sister drove from London to Milton Keynes to avoid having to use the replacement bus between Hemel Hempstead and Milton Keynes.

He said: "All the coaches at Milton Keynes made it seem like the Third World.

"There were about 20 to 30 coaches."

His sister, Julie McDonald, from London, said Railtrack's handling of the train lines was "disgusting".

She said: "You can't get a train these days or get to a station without it being cancelled or delayed.

"My husband works in London and without fail every day there is a delay."

Workmen

Virgin Trains has advised its passengers to take alternative routes where possible.

It said a change in health and safety rules meant it had not been possible to keep the line open - with trains crawling past workmen - as it had hoped.

West-Midlands based regional train firm Chiltern Railways is doubling its existing service and providing extra coaches between Birmingham Snow Hill and London Marylebone.

Midland Mainline is also operating a frequent service between London St Pancras and Sheffield, allowing passengers to change for services to Manchester.

Improvement work on the line has already been carried out at Euston, Willesden, Birmingham, Stafford, Ditton and in some areas of Manchester.

Stewart Francis, chairman of the National Rail Passengers Council, said the state of the rail network would mean disruptions being caused for years to come.

He said that "if you have not spent enough money on the infrastructure for so many years then clearly the backlog is going to build up and this is the problem facing Railtrack and Network Rail."