New quarantine rules are set to crush the UK travel industry for many more weeks, wrecking overseas holiday plans for millions.

The Independent understands the prime minister will announce on Sunday that travellers arriving in the UK by air, sea or rail will be obliged to self-isolate in stringent conditions for 14 days.

The aim is to reduce the rate of coronavirus infection. Covid-19 has been spread worldwide by international air travel.

The transport secretary hinted about the policy when interviewed by the BBC’s Andrew Marr Show on 3 May. Grant Shapps said: “I think it is important that [the sacrifices] we are asking the British people to make are matched by anybody who comes to this country.

“I am actively looking at these issues right now so that when we have infection rates within the country under control we are not importing.”

The move will wipe out almost all international travel for tourism and business to and from the UK for as long as it remains in force – which is likely to be at least until July.

Already, the pilots’ union has demanded that the government pays compensation for the financial damage the move will cause, while British Airways says it may ground all flights.

These are the key issues.

Define quarantine

According to the World Health Organisation (WHO), quarantine is: “The restriction of activities of, or the separation of, persons who are not ill but who may have been exposed to an infectious agent or disease, with the objective of monitoring their symptoms and ensuring the early detection of cases.

“Quarantine is different from isolation, which is the separation of ill or infected persons from others to prevent the spread of infection or contamination.”

How many people are coming into the UK?

At present, fewer than 10,000 people arrive each day – compared with around 300,000 daily arrivals before Covid-19.

Most are passengers flying into Heathrow – which handles between 40 and 50 arrivals a day – with a handful arriving at Stansted, Luton, Gatwick and Manchester.

A few dozen people turn up on the single daily Eurostar trains from Brussels and Paris to London St Pancras. And several hundred more arrive at British ports by ferry.

What is being proposed?

Almost everyone arriving from abroad at a UK airport, seaport or international rail station will be told that they must self-isolate for two weeks under stringent conditions. The rule is likely to be brought in at the end of May.

The only exceptions are expected to be arrivals from Ireland; some key workers; lorry drivers; flight, train and ship crew; and international transit passengers, the vast majority of whom will be connecting at Heathrow.

What is the process?

Inbound travellers will effectively be treated as though they have symptoms of coronavirus. They will fill in a form with their personal particulars, including passport data, stating where they intended to self-isolate, and providing contact details. They will be given a “stay-at-home notice” (SHN) telling them to stay indoors and avoid contact with other people.

After 14 days, if they do not develop symptoms, they will be allowed to join the general population.

Arrivals with no address in the UK will be told to stay in a hotel room, at their own expense – although very few people are likely to fall into this category.

How will quarantine be enforced?

Haphazardly. The authorities may maintain some sort of telephone contact, but mobile phones render that pointless for enforcement.

A system of random spot checks by inspectors is likely; they will call unannounced at the stated address. If the individual is not at home, they will be sought and prosecuted.

Will it work?

Even though almost all countries of origin have a lower incidence of coronavirus than the UK, it is possible that a small proportion of the arrivals from abroad may be carrying coronavirus and will be identified through the quarantine process.

But the World Health Organisation does not recommend quarantine for the infection phase in which the UK finds itself.

WHO says: “Introducing quarantine measures early in an outbreak may delay the introduction of the disease to a country or area or may delay the peak of an epidemic in an area where local transmission is ongoing, or both.”

In other words, if quarantine is to be used, it must be deployed early. Introducing mandatory self-isolation at this stage has been described as ”too much, too late”.

So why is it happening now?

Downing Street believes that introducing quarantine at the same time as other measures are being eased will send a message that the government is not lightening up too much or too fast.

The British public appears to be strongly in favour of the measures. Some high-profile figures, including Piers Morgan of ITV’s Good Morning Britain, have described the fact that there are no controls on arriving travellers as an outrage.

Mr Morgan tweeted: “So we’re doing this now, three months after the WHO declared Covid-19 a global health emergency, after we’ve let 100s of 1,000s fly in from corona-ravaged countries with no checks & after 55k+ people have already died in the UK? What a sick joke.”

In a Twitter poll conducted on behalf of The Independent with more than 2,000 self-selecting respondents, a very large majority – 78 per cent – were in favour of controls.

What will the effect be?

Quarantine will scupper the plans that airlines, airports, rail operators, ferry lines and travel firms have prepared for a gradual resumption of foreign holidays and international business travel.

A trickle of passengers – typically those returning from being stuck abroad – might endure a 14-day quarantine in order to be reunited with loved ones. But it is difficult to see that anyone would plan to travel abroad if they knew they faced two weeks in a far tougher lockdown than currently in force in the UK when they return. So the vast majority of planned trips will be cancelled.

Leading tour operators such as Jet2 Holidays and Tui were hoping to start offering package holidays at scale as early as mid-June.

Most big airlines, including British Airways, easyJet, Jet2 and Ryanair, were aiming to resume operations to and from the UK at or around the start of July. They now fear that “Project Lift-Off” will be put on hold indefinitely, further damaging future bookings.

What are the implications for travellers with flights or holidays booked?

Standard rules apply for now: from a consumer rights’ perspective, they must assume that the trip will go ahead unless and until it is officially cancelled by the operator.

Once a cancellation is notified, package holiday firms are supposed to refund within two weeks. Airlines must pay back passengers’ cash no more than a week after the non-departure.

Given the backlog of millions of cancellations, and the many more that the quarantine move will trigger, repayments are unlikely for several months.

How is the travel industry responding?

With astonishment and fury at the damage mandatory quarantine will cause to airlines, airports and holiday companies.

“This ludicrous step is surely one that should have been considered three months ago,” said Paul Goldstein, co-owner of Kicheche Safari Camp in Kenya.

“We should be weaning off it now, not introducing quarantine. It shows, yet again an almost derisory level of concern the government has for the travel industry.

“The travel industry has been gravely wounded by coronavirus, and now the government seems determined to kill it off completely.”

Abta, the trade association representing tour operators and travel agents, used more restrained language. A spokesperson said: “Travel and tourism has been severely impacted by the Covid-19 pandemic.

“Abta believes strongly that any new measures should be proportionate, led by the best possible medical and scientific advice and able to swiftly adapt to take into account any changes in this advice.”

Willie Walsh, chief executive of BA’s parent company, IAG, had previously warned: “If there is a 14-day quarantine, I would not expect us to be doing any flying, or very little flying.”

Karen Dee, chief executive of the Airport Operators’ Association, said: “Quarantine would not only have a devastating impact on the UK aviation industry, but also on the wider economy.

“Airports cannot survive a further protracted period without passengers that would be the result of quarantine measures.”

She called for a weekly review of the policy, saying: “If the government believe quarantine is medically necessary, then it should be applied on a selective basis following the science. There should be a clear exit strategy.”

The British Airline Pilots’ Association (Balpa) says tens of thousands of jobs in aviation have already been lost since the coronavirus pandemic began, and that mandatory quarantine will destroy many more. The pilots’ union has demanded that firms are compensated to help them save jobs.

Brian Strutton, the general secretary, said: “It can’t be right that aviation employees should get sacked to pay for government safety restrictions.

“Government imposed restrictions should be compensated for by government. Otherwise airlines will be forced to carry out their threats of redundancies.”

Inbound tourism to the UK will be written off. One tourism figure said: “Even if the measures are lifted after a week or two, incredible damage will have been done.

“The message to all tourists will simply be, ‘We do not want you,’ even if this action adds a million or two to the dole and leaves London as a ghost town.”

Is there any alternative to quarantine for identifying carriers?

Yes, at least according to the Austrian authorities, which are already operating a 14-day quarantine policy. Passengers arriving at Vienna airport can avoid it by attending a medical centre near the terminal and undergoing a test for coronavirus.

Participants must pay €190 (£166) and wait for three hours for the results, but if they pass they have a “get out of jail free” card and need not self-isolate.