Hundreds of passengers were left stranded on Eurostar trains after services were suspended because of a person near the track.
Trains were held after the incident at Dagenham Dock station which began at around 8pm, the company said.
A Eurostar spokeswoman said the decision to suspend travel had been made by British Transport Police before the lines were reopened at around 11pm.
A number of passengers vented their frustration at the delays.
Passenger Becca Mundy said on Twitter: "Seriously @Eurostar we've been on the 7.34 for over 2 hours now, no movement at all. Surely it can't take this long to resolve issue?"
Emma Truswell added: "Ways I did not expect to be spending my Friday evening: stuck on the Eurostar somewhere near Rainham."