One of the tunnels used by the train company is back in operation - but Eurostar are warning of further delays and restrictions.
ADVERTISEMENTEurostar services have restarted, but warnings of further delays and busy stations remain in place.
On Saturday, cancellations saw many people’s travel plans thwarted.
Eurostar has blamed “unprecedented” flooding, but now says the situation has been brought under control.
“At least one tunnel can now be used” on the train line, they explained.
While the first train left London for Paris at around 8 am local time, speed restrictions still apply and uncertainty surrounding the second tunnel will likely mean that further disruption could be possible.
In a statement, Eurostar said: “Flooding in the Thames tunnels has been brought under control by Network Rail High Speed, meaning at least one tunnel can now be used and a full service can operate.
“There will be some speed restrictions in place in the morning which may lead to delays and stations are expected to be very busy. Unfortunately, this unprecedented event has caused major disruption to customers today,” they said.
“Customers are encouraged to visit the Eurostar website for more information on their journey and compensation entitlement.”
A spokesman for HS1, which runs the route between London and the Channel Tunnel, released a statement saying: “Flooding in the Thames Tunnel is being resolved by Network Rail High Speed and the HS1 line will be operational in the morning.
"We understand how frustrating this has been for passengers and apologise for the inconvenience caused at such an important time of the year.”
HS1 or Eurostar have not revealed what initially caused the leak.