A suspected illegal immigrant was arrested after being found on the outside of a Eurostar train – which had been travelling through Kent at 186mph.
The man was detained by British Transport Police officers after being discovered at Ebbsfleet International Station near Gravesend in Kent.
He was intercepted at the station on a Brussels to London service just before 7pm last Thursday.
Eurostar trains can reach speeds of up to 186mph while in service.
A Eurostar spokesman said: "We can confirm there was a suspected illegal immigrant on the outside of the train, but cannot comment further on the details. The matter was dealt with by the British Transport Police."
The BTP was unable to confirm reports that the man originally boarded the train in France and was found in a section between carriages.
A BTP spokesman said: "On April 23 at Ebbsfleet International, a suspected illegal immigrant was arrested by BTP officers and dealt with by the UK Border Agency."
Earlier this week, French immigration minister Eric Besson vowed to clear Calais of groups of illegal immigrants waiting to cross the Channel to the UK hidden in lorries, ferries or freight trains.
Mr Besson said he would order the removal of a squatter camp which evolved after the closure of a French Red Cross reception centre at nearby Sangatte more than six years ago.
He also challenged the UK authorities to share responsibility for solving the problem - and then ask themselves why migrants from places such as Afghanistan, Iran, Somalia and Sudan believe that the UK is such an opportunity for them.
A UK Border Agency spokesperson said: "The UK continues to work with France in fighting illegal migration and our shared determination has already created one of the toughest border crossings in the world.
"State-of-the-art technology such as carbon dioxide and heartbeat detectors and moving our border controls to France means we can turn people away before they even step foot on British soil.
"Last year UK Border Agency staff worked tirelessly at our French and Belgium controls, not only searching more than one million lorries but also stopping 28,000 attempts to cross the Channel illegally."