The race is on: British holidaymakers in France, Malta and the Netherlands, among other places, have until 4am on 15 August to return to the UK if they're to avoid two weeks of mandatory quarantine.
In another devastating blow to the travel industry, the government announced that these countries, along with Monaco, Turks & Caicos and Aruba, have been taken off its list of travel corridors from where arrivals are exempt from the blanket 14-day self-isolation policy.
There are currently around 500,000 British travellers in France, many of whom are desperate to get home before the deadline as they cannot afford to miss out on work or disrupt their children's return to school by quarantining.
Read below for the latest updates on the great travel exodus.
Travellers who are tempted to ignore the FCO advice and travel to France regardless could face four weeks of quarantine - two weeks when they arrive in France and two weeks when they get back to the UK.
France said it would impose quarantine restrictions on travellers arriving from the UK in response to the UK removing it from the quarantine-exempt list.
“It is a decision that we regret and one that will entail reciprocal measures in the hope that we can return to normal as quickly as possible,” said Clément Beaune, France's Europe Minister.
The UK isn't the only one imposing travel restrictions. Latvia has announced that, as of 14 August, all UK arrivals will have to quarantine for two weeks.
The country has imposed the restriction on all countries with a Covid-19 infection rate of 16 or higher per 100,000 residents The UK's rate is currently 18.5.
P&O Ferries has warned passengers that they should have a valid booking before turning up to the port in Calais today.
The company said it expects the port to be "busy", tweeting: "To avoid disappointment at the port, please book in advance.
"In light of the quarantine measures announced, we expect an influx of UK residents attempting to travel today. Please ensure you leave enough time to clear border controls and check-in queues."
Skyscanner says that, in the last 24 hours, it has seen an unprecedented number of redirects for flights departing from France to the UK as travellers scramble to get home.
Despite the surge in demand, there are still options available; the flight comparison site is still selling seats on a Nice to Heathrow service departing today at 9.10pm, currently priced at £222, and tickets available for a Paris Charles de Gaulle to Heathrow flight departing 9.40pm for £190 one-way.
A search on Skyscanner shows there are still last-minute flights from Amsterdam to London for travellers looking to return today.
EasyJet has a 7.10pm departure to Gatwick and a 7.20pm departure to Stansted, priced at £168 and £152 respectively.
British Airways has a slightly later departure to Heathrow at 9.20pm, but it's more than double the price at £356.
Stena Line's final departure from the Hook of Holland to Harwich today leaves at 10pm but doesn't arrive in the UK until 6.30am on Saturday - too late for travellers to avoid the quarantine.
However, the company has had confirmation from the Department for Transport that people travelling from exempt countries can continue to use the route as an exit point from the EU, as long as they don’t stop in the Netherlands on the way.
Brits due to go on holiday to France, the Netherlands and Malta should be aware of their rights.
Emma Coulthurst, travel commentator from holiday price comparison site TravelSupermarket, says: "Now that the FCO advice has changed to essential travel only for these countries, if a flight or train (e.g. Eurostar) or ferry is cancelled as a result, you are legally entitled under EU 261 to your money back within seven days.
"However, your flight or train may still go ahead despite the FCO rule change. Transport providers are allowed to keep operating for people who still want to travel.
"You will need to look to change your journey to a different future date, when you can hope that the rules will have changed (see below for more info on this). If you had travel insurance in place before the pandemic became a known event back in mid-March or you have had an annual policy in place pre mid March which was automatically renewed, then you might be covered."
Those with package holidays booked to these countries have a greater level of protection and should be able to cancel and get a refund under the Package Travel Regulations.
Some travellers are so desperate to get back before the quarantine deadline that they're resorting to chartering a private jet.
PrivateFly, a UK-based private jet provider, reported it received three times the number of enquiries and bookings for flights out of countries set to be added to the UK’s quarantine list compared with 24 hours previously.
Adam Twidell, PrivateFly CEO, said: “Following the changes to the UK’s quarantine list overnight, we’ve received a surge in demand for private jet travel out of affected countries, with three times the average number of enquiries and bookings for flights to the UK from France, The Netherlands and Malta, before 4am on Saturday morning.
“We’ve also had a number of enquiries from clients booked to travel to these destinations in the coming weeks to change their travel plans in order to avoid quarantine zones.”
As well as those returning from the affected countries, thousands of travellers returning from quarantine-exempt countries are confused about the rules should they pass through France to get back.
The rules state that, if you're in a private vehicle, ie a car, "You don’t need to self-isolate if you travel through a non-exempt country and you don’t stop in the country.
If you do make a stop, you don’t need to self-isolate if: no new people get into the vehicle; no-one in the vehicle gets out, mixes with other people, and gets in again."
Equally, if you travel by train, ferry or non-direct flight, you don’t need to self-isolate if, during your transit stop in a non-exempt country: no new passengers get on; no one on-board gets off and mixes with people outside; and/or passengers get off but do not get back on.
However, "If your journey involves a transit stop in a country not on the list, you will need to self-isolate when you arrive in England if: new passengers get on; or you or other passengers get off the transport you are on and mix with other people, then get on again."
Many Brits who are heading back early are confused and frustrated by the sudden policy change.
Pilot Duncan Ross, who is among those cutting a trip short, called it "madness".
It's not just those in France who have been hit by the sudden quarantine rule change. Holidaymakers in Malta and the Netherlands are also struggling to get home.
From Malta, all today's direct flights have sold out, but routings are available via Italy. Cheap deals are also on offer via Portugal – but changing planes there would trigger a quarantine obligation, making the early exit pointless.
Fares from Amsterdam have also soared. Between the Dutch capital and Edinburgh, the lowest fare on Friday is £334.
Eurostar is currently running a reduced service from Paris to London St Pancras International. There is still some availability on both the 15.13 and 17.13 departures today, priced at £268.50 (standard premier) and £209.50 (standard) respectively.
The World Travel and Tourism Council (WTTC) has deplored Britain’s quarantine extension.
Gloria Guevara, the chief executive, said: “WTTC is deeply disappointed that thousands of British holidaymakers have had their holidays ruined, now the UK government has added more countries to its quarantine list, including popular summer holidays destinations, France and Malta.
“While we agree public health should remain the top priority, this move will crush what little confidence there is left in the fragile travel and tourism sector."
