The services use Japanese-built Class 395 140mph Javelin trains
The new high-speed train service operating between Kent and London St Pancras has been officially launched.
The Japanese-built Class 395 Javelin trains, run by Southeastern, can reach speeds of up to 140mph.
The first of the new weekday services arrived on time at St Pancras at 0551 GMT, 37 minutes after leaving Ashford.
On board the first train out of London at 0625 GMT was Transport Secretary Lord Adonis and double Olympic gold medallist Dame Kelly Holmes.
They made the early morning journey to Rochester and back on a 508-passenger Javelin named after Dame Kelly.
It was one of 29 of the Hitachi class 395 trains that will run on Southeastern routes, using sections of the London to Folkestone Channel Tunnel rail link now known as HS1.
They were greeted at St Pancras by Prime Minister Gordon Brown, who hailed the start of the service.
"This is a great day for St Pancras and for Kent, rail services in this area and for the UK," he said.
"This is also a momentous day in the long and glorious history of British railways."
The new trains, which cost about £6m each, have been running on a limited preview service basis since June, with a full service starting on Sunday.
The introduction of the trains coincides with the launch of a new rail timetable for Southeastern - the biggest change in 40 years.
It will provide an extra 200 trains across the region and increase capacity on the network by 5%.
The rail company said the service would cut journey times from Dover to London from more than two hours to 69 minutes.
However, passengers using the Javelin commuter trains will have to pay higher fares.
Gordon Brown said the launch of the Javelin trains was "a great day for Britain"
A peak-time Ashford-London return will cost £48.70, compared with the usual fare of £40.60.
London-Folkestone will be £52.50 rather than £44.40.
Lord Adonis said: "These fantastic new services, made possible by the government's investment in this £5.8bn high-speed new line, are changing the transport map of Kent.
"Journey times have shrunk dramatically, bringing regeneration and new opportunities for investment.
"This shows the potential of high-speed rail and we now must consider what it can do for the rest of the country."
Southeastern managing director Charles Horton said it was a "great day for the industry".
"Today marks the most important day in our franchise. We have been working hard since 2006 to achieve this goal.
"To be able to bring in the trains six months early as part of a preview service over the summer is testament to the teamwork we have put in with Hitachi, HS1 and Network Rail."