UK residents in India are paying for private charter flights in a desperate bid to get home before a travel ban is imposed.
On Monday Britain took the "difficult but vital decision" to add India to its red list of countries after confirmed cases of the Indian Covid-19 variant in the UK rose to 103.
From 4am London time on Friday, returning British citizens will have to pay to quarantine for 10 days in a government-approved hotel, while others will be refused entry.
Concerns are rising that the variant, first identified in India, could be behind a devastating wave of new infections in the subcontinent.
Some scientists said the British government was too slow to act after the first case in the UK was identified on February 22.
Meanwhile, Suresh Kumar, the chairman of travel agency Indra Travel, told The National there was "no chance" the majority of British citizens in India would make it back to the UK before Friday.
He said a consortium of travel agencies was arranging one-way charter flights, at £1,500 ($2,090) per passenger, to meet the demand.
“People are desperate to get back,” he said. “The limited seats that are available are being charged at four times the value. An economy ticket from Delhi to London would normally cost £400 – it’s close to £2,000 now, if you manage to get one.
“We’re faced with a lot of people stranded in India because there’s no availability of flights.”
Prerit Souda, UK spokesman for the Indian National Students Association, said Indians hoping to attend classes in the UK were reconsidering because of the potential price.
"The cost of quarantine is causing alarm and concern and, from a psychological point of view, there is the feeling of being cut off," he told The National.
“The cost of more than £1,700 to stay in quarantine is not affordable for most students.”
Mr Souda estimated there were up to 30,000 Indian students studying in the UK, and said hundreds more were planning to come to Britain as the country emerged from lockdown.
His figures include prospective students and some who are enrolled with UK universities but have until now been studying remotely.
“They had hoped the UK might be doing better, but now India is in trouble,” he said.
The UK’s red list now comprises 40 countries. Since hotel quarantine measures came into force on February 15, only Portugal has been removed.
That has compounded fears that India could remain on the travel-ban list for months. UK authorities base red-list additions on factors such as infection and vaccination rates.
India is recording more than 200,000 new cases per day, and the health system is said to be crumbling under the weight of new infections, with Covid-19 patients housed in sleeper trains converted into clinics.
The country has vaccinated 7.5 per cent of its 1.3 billion population, Our World in Data said.
British Prime Minister Boris Johnson cancelled his trip to India next week, where he had hoped to boost ties between the nations as part of his post-Brexit trade vision.
Sharon Peacock, the director of the UK genetic-sequencing operation, said the variant detected in India, which has a “double mutation” that some scientists believe could help it to evade immunity, “has been around for some time”.
It was first sequenced in October and spotted initially in the UK on February 22. However, there is not enough evidence to suggest it is more dangerous than previous strains.
Prof Peacock said the UK was taking a cautious approach while scientists decided whether the variant was to blame for India’s second wave.
“The question is whether this is associated with the variant, with human behaviour (large gatherings, and/or lack of preventive measures, including handwashing, wearing masks and social distancing) or whether both are contributing,” she said.
Prof Sir Mark Walport, former chief scientific adviser for England, said the decision to place India on the red list came too late.
"What's absolutely clear is that this variant is more transmissible in India," he said.
“You can see that it's becoming the dominant variant and the other concern … is that it has a second change in the spike protein, which may mean that it's able to be a bit more effective at escaping an immune response, either a natural one or vaccine-induced one. So there are good reasons for wanting to keep it out of the country, if at all possible."
Education Secretary Gavin Williamson defended the government’s decision to wait until the end of the week for the changes to take effect, and said it was “standard practice to give a short window”.
“The government continuously reviews the data … sadly, India is one of those countries that have to be added,” he told Sky News.
“We have to remain vigilant against new variants – that’s why we have to place India on the red list.”
Britain’s main opposition Labour party said the government should have acted sooner.
“It’s not good enough to try and shut the door after the horse has bolted, by adding countries on to a red list when it is too late,” Shadow Home Secretary Nick Thomas-Symonds said.
UK health authorities said the Indian strain was a “variant under investigation”, but this could progress to a “variant of concern” if it is discovered to spread more easily or undermine vaccines.
Prof Danny Altmann from Imperial College London said that new variants should be treated with caution as vulnerable people could be “caught out” if the strain was able to evade immunity.
“We are still vulnerable, and some people in our population are still vulnerable – what I mean by that is the Indian variant, for example, certainly has a mutation like the ones that evade the best neutralising antibodies,” he said.
“If you have a population where at least half of us have had zero or one dose of [the] vaccine, some won’t have made a very good response [...] because perhaps they are very old or obese or unwell.
“We still have a very large vulnerable population who can still be caught out by variants like this.”