A migrant was stopped inside the Channel Tunnel walking towards the UK, according to Eurotunnel.
The Sudanese national was arrested a few kilometres from the British entrance of the 50.5 km (31-mile) tunnel on Tuesday.
A spokesman for Eurotunnel said the person “almost succeeded in walking through the tunnel”.
The train operator held an “unplanned” inspection on the same day, which led to four-hour delays.
A 40-year-old man, of no fixed address, has been charged with causing an obstruction to an engine or carriage using the railway and was due to appear at Medway Magistrates’ Court on Thursday.
The incident came on the same night that migrants made about 600 attempts to enter the Channel Tunnel.
About 180 people were caught inside the site, with 20 arrested.
However, intrusions were down to about 400 a night on Tuesday and Wednesday, according to Eurotunnel.
It said additional efforts to secure the French terminal were almost complete and attempted intrusions by migrants were now being brought under control.
There have been thousands of attempts to access the terminal at Coquelles in recent weeks, with nine people killed trying to get into the tunnel since June.
Foreign Secretary Philip Hammond said 100 more guards would be deployed in the Eurotunnel terminal following a meeting of the government’s emergency Cobra committee on Monday.
He also announced a “much improved level of co-operation and collaboration with Eurotunnel” and a UK Border Force and French police presence in the Eurotunnel control room at Coquelles.
It is estimated there are some 3,000 migrants in the Calais area and many are continuing their attempts to reach the UK by crossing the Channel.
Some try to stow away on lorries headed for the Eurotunnel, or climb or cut security fences to try to hide on Eurotunnel shuttles.