Civic chiefs offered a warm welcome to the arrivals, who they hope will boost the city’s tourist economy. It has been hammered by three lockdowns and restrictions on foreign visitors.

London minister Paul Scully told the Standard: “As a global city, London has so much to offer for international travellers; the best shopping, theatre, cuisine and historical landmarks. That’s why we should all back our #LetsDoLondon campaign to remind our international friends how much we’re missing them and the fantastic welcome Londoners are here to give.”

There were scenes of joy at Heathrow on Monday as families kept apart by the pandemic, some for nearly two years, were finally reunited. At Terminal 5, dozens of families were waiting to see their relatives, who live in the US, as restrictions in both countries have made travel between them almost impossible before today.

Sharon and Ray Wilson, from Surrey, were waiting for their son, daughter-in-law and two grandchildren who were flying in on the first flight from New York to London at 6.30am.

They had not seen their family for 22 months and were looking forward to celebrating their grandson Johan’s third birthday during the visit.

Mrs Wilson told the Standard: “It’s been incredibly difficult. FaceTime all the time but it’s not the same is it. I can’t hold in my excitement.”

Mr Wilson added: “Usually we go out there three times a year so it’s been very difficult. We just can’t wait to spend time as a family again. It’s been way too long.”

Michael Blake, 71, from Hampstead, was waiting for his son Elliott and grandson Jack, eight, to arrive from New York.

His son had put the family flight back a week so they would not have to isolate on arrival.

Mr Blake said: “We usually see each other several times a year so it’s been a difficult 18 months. My son is fully vaccinated now and we are very excited to finally see him, our daughter-in-law and grandson.”

The new rules, exempting the double-jabbed from the US and EU, apart from France, from having to self-isolate came into effect at 4am today. They have not yet been met by a reciprocal easing across the US of restrictions for travellers from the UK.

But some tourists were also already flying into Britain from America.

Dara Osei, 28, said: “I know a bunch of people in London and I’ve wanted to come for a while but obviously it’s not been possible in the pandemic.

“I’m most looking forward to going out. To visiting all the restaurants and clubs London is famous for.”

Mayor Sadiq Khan said: “We’ve all been looking forward to having the freedom to travel again. Not only will this boost London’s economy, it will lift our spirits as it means that people are once again able to see loved ones based abroad after so long spent apart.

“But with the continued risk of new variants emerging, it is important we take a cautious approach, and that the Government ensure an effective system of ensuring travellers are fully vaccinated is in place.”

Tourist attractions were also gearing up for more visitors.

Pete McGowran, chief yeoman warder at the Tower of London, said: “It’s great to see the capital opening up and we can’t wait to do our bit for tourism in London by showing overseas visitors some of our history again.”

The Tower’s audience is generally two-thirds international tourists.

Tracy Halliwell, director of tourism at Visit London, said: “The USA is London’s number one market for visits and spend, with 2.2 million visits in 2019 and £2 billion spent, so it’s fantastic that this key tourism market can now start to reopen.”

Massive increase in bookings

The new travel rules have seen has led to a "300 per cent increase" in bookings to the US, Airlines UK chief executive Tim Alderslade said as he welcomed the change.

But, he said, adding more tiers to the travel system, as Cabinet ministers are currently considering, would over-complicate international travel, describing the amber list as a "red flag for travellers".

Mr Alderslade told Times Radio: "I think the announcement this morning is very welcome - there will be an uptick in bookings.

"We've seen from the US around a 300 per cent increase in bookings to the US - but we've got to somehow try to find a way to get more countries on the green list and we absolutely should not be going down the road of adding more tiers to an already very complicated international travel system."

"I think the problem with the US is that we can't travel there, so the Biden administration still will not allow Brits and Europeans to enter the US, so it will be slightly curtailed because of that," he added.

"I think the big issue for us as an industry is the green list... amber at the moment is a red flag for travellers, it's a glaring warning sign because of the worry that people have that they will either be stranded overseas or they will have to quarantine either in a hotel or a home for 10 days."