This is the time of year when Indians in their thousands make their way to London to escape the searing heat of summer at home and do their shopping in Oxford Street, but they have to be aware that on arrival they are required to go into self-isolation for 14 days.

According to the rules laid down by home secretary Priti Patel that will come into effect on Monday, anyone found not observing self-quarantine risks a £1,000 fine and deportation as well.

British Airways argues foreign visitors will not want to come to the UK, typically for a two-week break, if they have to remain cooped up inside a hotel room for the entire period.

BA — an important carrier for UK-India travel — pointedly declined to join a meeting between Priti and the travel industry to discuss the quarantine last Thursday.

According to the Sunday Times, BA is instead preparing to lay down a legal challenge against the home secretary’s order.

The airline’s parent company IAG sent a pre-action letter, which is the first stage in a judicial review, to ministers ahead of the measures coming into effect.

The letter, seen by the Sunday Times, argues the restrictions are disproportionate.

It states: “In our view, the government has failed to identify a valid justification for the blanket nature of the regulations, especially given the extremely severe nature of the self-isolation provisions that apply.”

The letter sent to the Procurator General Sir Jonathan Jones was also signed by BA’s budget rivals easyJet and Ryanair.

IAG chief executive Willie Walsh described the government’s quarantine policy as “terrible” and warned it has “torpedoed our opportunity to get flying in July”.

He told Sky News on Friday: “We think it’s irrational, we think it’s disproportionate, and we are giving consideration to a legal challenge to this legislation. We are reviewing that with the lawyers later on today.

“I suspect there are other airlines who are doing so because it’s important to point out there was no consultation with the industry prior to enacting this legislation. We do believe it is an irrational piece of legislation.”

BA has announced its intention to pull out of Gatwick, London’s second airport, and sack 12,000 of its 42,000 staff. Also, according to the Sun, BA has told the pilots’ union Balpa that all 4,300 of its pilots will be fired and re-hired if current employment negotiations break down.

Meanwhile, it was confirmed by the Bank of England that it has lent £300 million to IAG as part of its emergency pandemic funding.

It does not look though that Priti, who almost certainly cleared the quarantine idea with the Prime Minister Boris Johnson — he also backed her when the home secretary was accused of bullying senior civil servants — is set to budge.

In the Commons, former Prime Minister Theresa May, who once forced Priti to resign as international development secretary, was ignored when she opposed the quarantine: “Instead of measures to close Britain off from the rest of the world, why is the government not taking a lead in developing an international aviation health screening standard to save jobs and ensure Britain is open for business?”

Priti said: “The answer as to why we are bringing in these measures now is simple: It is to protect that hard-won progress and prevent a devastating resurgence in a second wave of the virus.

“What we are seeking to do is control the spread of the virus because we do not want a second wave of this virus.”

Indian doctors in the NHS predict that a second wave this winter is inevitable.

The quarantine plan will be reviewed in three weeks. There could also be “air corridors” with some European countries — but probably not with India — where the pandemic has abated.