BRITAINs first full domestic high-speed rail service opened for business this morning - slashing journey times but bumping up ticket prices by around 20 per cent. A full timetable of the Japanese-built 140mph trains is now running from London to Kent, on sections of the High Speed one (HS1) Channel Tunnel rail link. But passengers have to pay more to use the super-fast trains, operated by the Southeastern train company, than those using the 'normal services. And even those Southeastern customers not using the 508-passenger Javelins will find their fares going up by more than the national average in January 2010 as part of Southeasterns franchise agreement. The Javelins were first introduced in limited form in June this year as part of a 'preview service. Those taking advantage of the new trains will find that a peak-time Ashford-London return will be 48.70 compared with the normal fare of 40.60, while London-Folkestone will be 52.50 rather than 44.40. Ashford is around 50 miles from London. PM Gordon Brown today hailed the service and promised to invest 20 billion in railway infrastructure in the next few years. Mr Brown also announced that the Government would publish plans by the end of March for a North-South high-speed rail network. The Prime Minister, just back from a tour of Afghanistan, was speaking at St Pancras International Station in London, where the first weekday services of the full Javelin train operation run by the Southeastern train company started today. Daily Mail Mr Brown greeted his Transport Secretary Lord Adonis and double Olympic gold medallist Dame Kelly Holmes, who had travelled on one of the Javelin trains today. The train has drastically reduced journey times from Kent into London, although Southeastern passengers are all paying more, both to use the service and in other fares to pay for the investment. Mr Brown, speaking on one of the Southeastern platforms at St Pancras, said: 'This is a great day for St Pancras and for Kent, rail services in this area and for the UK. 'This is also a momentous day in the long and glorious history of British railways. Mr Brown said the railways have been essential for Britain and will always be essential to the country. He said: 'I know some people who think this is not the time to be investing in infrastructure but I believe it is essential to do so and we will be investing 20 billion in our rail infrastructure in the next few years. HS2, a Government set-up company to look into the feasibility of a north-south high-speed rail line, is due to report to the Government with its findings by the end of this month. Mr Brown said today that following receipt of the report, the Government would be publishing its plans for a high-speed line by the end of March. The Prime Minister said that later today Lord Adonis will be announcing the electrification of rail lines between Manchester and Liverpool and Preston. The train that Lord Adonis and Dame Kelly travelled on today was named after the Olympic champion and is one of 29 that will form the high-speed service, running on part of the Channel Tunnel high-speed London to Folkestone line, which is now known as HS1. Dame Kelly said today: 'I am from Kent so this is a very proud day for me. For my name to be on a train is really something. The new trains have been running on a limited basis since June, with a full service starting yesterday, and today it provided workers with their first opportunity to take advantage of reduced journey times to many Kent destinations. For example, the Ashford to London journey time comes down from well over an hour to just 37 minutes. London to Ramsgate times - now 81 minutes - are reduced by an average of 49 minutes, while the new London-Dover time of 69 minutes represents a 47-minute saving. Customers seemed pleased with the new service today, although they are paying more to use it than they would travelling on the 'normal trains. Operations manager Mike Arnold, 40, from Chatham, Kent, said as he arrived at St Pancras today: 'Its fine. Its cool. Another passenger arriving at London, civil engineer Russell Naylor, 52, said: 'The new service is very good. Mr Naylor, from Lympne, Kent, who was travelling from Ashford, said he normally travelled in on a Sunday evening to London but was more likely to take the Monday morning services from now on. One passenger who was less enthusiastic about the new service was budget manager Paul Tierney, 57, from Chatham, Kent. He said: 'The train was cold. I am feeling chilly. Passengers are paying more to use the new service and under the terms of Southeasterns franchise, annual fare increases for its passengers are higher than for other train companies, to take account of the extra investment and the fast trains. Southeasterns regulated fares, which include season tickets, will go up by 1.6 per cent in January while some unregulated fares, which include some off-peak journeys, will rise by as much as 7.3 per cent. Daily Mail