By Paul Sandle
LONDON (Reuters) - A Sudanese migrant walked the 50-km (31-mile) Channel Tunnel from France, dodging high-speed trains and evading security guards before he was stopped just short of the British entrance and arrested, police said.
Thousands of people from Africa and the Middle East have been trying to flee makeshift camps in the French port of Calais and enter Britain by jumping onto lorries or hiding on trains, disrupting cross-Channel freight and passenger traffic.
British police said Abdul Rahman Haroun, 40, was found close to the British entrance to the tunnel near Folkestone in southeast England on Tuesday evening.
Police said he had been charged with "causing an obstruction to an engine or carriageway using the railway".
British Prime Minister David Cameron said more fencing, guards and sniffer dogs were being sent to beef up security at the terminal in Calais.
"We are making progress but there is a lot more to do, including better security in the tunnel itself," Cameron told Sky News on Friday. "We will oversee these improvements and they will take place in the coming weeks and days."
The U.N. refugee agency UNHCR said conditions at Calais were "appalling" but the "mere 3,000" people there were manageable, and more security would not help.
This year Britain has turned down 10 requests from France to take responsibility for people with close links to Britain, who are allowed under European law to seek asylum in France and then transfer to Britain, UNHCR's Europe director Vincent Cochetel said.
Britain had far fewer asylum seekers than France, and two-thirds of them arrived via legal channels, he said.
"There is not a significant wave of people coming to the UK," Cochetel added.
Cameron's government said on Friday it was working with the French government and operator Eurotunnel (PA:GETP) to resolve the crisis. It said more than 39,000 attempts to cross the Channel illegally were prevented in 2014 to 2015, more than double the previous year.
Eurotunnel has launched an investigation into this week's tunnel incident, which it said had caused "delays for customers and significant economic loss".
"A criminal intrusion into the Channel Tunnel is an extremely rare incident. It is both illegal and highly dangerous," a spokesman for Eurotunnel said in a statement.
"Eurotunnel hopes that the full force of the law will be used to demonstrate that an attempt to enter the Channel Tunnel poses not only a significant risk of injury or death, but also precludes any possibility of entering the UK to claim asylum or to find work."