Charlotte Liddell, a bride-to-be, was on the way to her own hen party when her group discovered the cancellations.

Others in the party are already in Paris, having flown from northern England.

The London resident will fly from Leeds Bradford Airport and hopes to be in Paris this evening.

“It’s the hen do without the hen!” she said. “We’re very upset, but it’s so out of our control.”

Fran Birch, who will be a maid of honour, said: “We’ve got all the decorations with us.”

About the bomb, she joked: “It’s from World War Two. Just let it lie.”

Tens of thousands of passengers are stranded at either end of the London–Paris Eurostar link following the discovery of a wartime bomb at St-Denis, a few miles north of Gare du Nord in the French capital.

The closure has happened on the busiest day of the week for Eurostar. Besides large numbers of business passengers shuttling between London and Paris, Friday is the key day for leisure travellers heading for a weekend away.

Eurostar says all its 32 trains on the link are cancelled, leaving 25,000 passengers out of position.

Charlotte Kidd, who travelled to London from Bath last night to get to Disneyland Paris for her 30th birthday this weekend, said she was still hopeful of getting there in time.

She said: “We’ve got two hours. If not, we’ll try and get there some other way.”

Emma Roe, part of a group of eight friends, said they were looking up flights to go “maybe to Amsterdam from Luton, just somewhere else”.

“There’s no booking until 6pm tonight.

“We’re all parents, so we don’t want to lose our free weekend.”

After earlier cancelling a dozen trains, Eurostar has now cancelled all trains on Friday between London and Paris.

The train operator said in a statement: “Due to the discovery last night of an unexploded bomb from the Second World War during work carried out on the tracks in St Denis (north of Paris), traffic has been completely halted to and from Gare du Nord.

“As a result, all Eurostar trains are cancelled to and from Paris today.”

Eurostar has announced that all its services between London and Paris will be suspended throughout Friday after the bomb discovery.

The train operator had previously told passengers to expect disruption because of “an object on the tracks”, and advised them to “change your journey for a different date of travel”.

Services will only be permitted to resume once “mine clearance operations” by the French police are completed, the spokesperson added.

The Independent’s travel correspondent Simon Calder reports:

The two unluckiest Paris weekenders have been caught up in the Eurostar chaos.

Joe and Laura Booth, from Hull, were supposed to be flying to Paris last month from their local Humberside airport for a birthday celebration for Laura. But their airline, KLM, wrongly denied them boarding – falsely claiming Laura’s passport had expired.

They rescheduled the trip – but booked on Eurostar from London because they did not trust the airline to get them to the French capital.

Joe Booth told The Independent: “It was chaotic at St Pancras this morning. We got checked in 4.45am, into departure lounge and didn’t hear a thing about a delay until 15 minutes before we were due to depart at 6.01. So we had to think on our feet – the queue for the information desk was outrageous.

“We checked online for the French public transport pages and it was suggesting lines would reopen at 9 or 10am French time.

“With this in mind, [we] took a punt and paid £600 for fresh tickets – the only ones we could find before this evening, in first class on the 9.31am Eurostar to Paris.

“The 9.31am has already been cancelled but we’ve moved the booking to the 12.31pm.

“We are currently in the first class lounge hoping and praying lines reopen this morning and we get there around 4pm French time.

“If the 12:31 is cancelled, then I think unfortunately it’s back home again. We’ve got too much luggage to fly really, well at least as cabin bags, we would have to check some into the hold.

“But with thousands of people in the same position, we have probably missed the boat now on a flight for today.

“We’ve booked and paid for a floating restaurant tonight as a treat given all the stress of last time. If we don’t get there before 5pm French time, we are probably going to lose that and been honest, anything after 5pm would render the trip pretty useless anyway.”

Fabien Villedieu, leader of the SUD rail union shared a picture of the unexploded bomb on social media, which he said weighed 300kg.

The bomb which has prompted chaos on the Eurostar was discovered at around 4am by workers doing earth-moving work near the Seine-Saint-Denis of northeast Paris.

Minesweepers were sent to the site, and their operation to guarantee the area is safe is still going on.

It isn’t uncommon for bombs left over from the World Wars to be discovered in France – but to find them in such a people-packed location is rare.

French transport minister Philippe Tabarot told broadcaster Sud Radio that local residents and people near the train stations should have “no fear” of a risk of explosion, stressing the procedures in place for defusing and removing such bombs.