In the Nineties I was visiting Hong Kong as Secretary of State for Defence. I was invited to go up in a helicopter to view the island in the bay, many miles from the city centre, where the new airport was starting to be built.

From the air I could see no convenient flat islands, only several with steep, wooded hills. My hosts patiently explained that the next time I came to Hong Kong they would be flat islands with the hills sliced away and used as infill.

And so it turned out to be. Hong Kong now has a marvellous international airport with all flights approaching across the South China Sea and with millions of Hong Kong residents freed from the pollution, excessive noise and other environmental damage normally associated with great airports.

It is not just Hong Kong that has taken a historic decision to move its main airport and create new terminals and runways that can meet the demands of the future without destroying the quality of life of residential communities.

Paris in 1974, Munich in 1992, Athens in 2001 and Bangkok in 2006 are just some of those that have had vision and none has regretted it. As ministers announce the next stage of the Government’s aviation policy today, it is time that London did the same.

If we were starting from scratch, Heathrow would probably be the last place we would choose to build Britain’s premier airport. It is surrounded on virtually every side by residential communities. All the flight paths are over the homes of millions of people, with many crossing directly over the centre of London.

Of course, a decision to build a new airport for London in the Thames estuary would take years, be very expensive and would, no doubt, be opposed by various interests. But that was true in every other world capital where people of vision not only understood but were able to explain that the major advantages far outweighed the significant problems.

What would be the advantages? First, for the airlines and passengers that need to fly, there could be as many runways as were required. Flights could arrive and depart at all hours.

Secondly, all flights could approach from the North Sea and up the Thames estuary, with minimal disturbance to the public on the ground.

Thirdly, a high-speed rail-link could ensure that passengers could reach central London in around 20 minutes. Crossrail could be extended to connect with routes to the new airport.

It is worth remembering that a substantial proportion of passengers who land at Heathrow merely get off the plane in order to connect with another flight going to another destination. For millions of such passengers there is no conceivable benefit from landing at Heathrow as they never leave the airport.

If such a new airport removed the need for Heathrow, this would release for residential, commercial or industrial development no fewer than 2,500 acres of prime land close to the M4 which, itself, could create thousands of new jobs.

Of course, there are potential downsides and these would have to be thoroughly investigated before any final decision could be reached.

The construction costs would be many billions of pounds — but some of that could be recovered from the release and development of prime land at Heathrow. If costs have been able to be absorbed in countries poorer than the UK, this should not be insuperable, especially if spread over a number of years with much of the cost falling on the private sector and not on the taxpayer.

There are also environmental challenges that would have to be addressed. The estuary is the habitat for many thousands of wetland birds. It has also been suggested that there could be an increased risk of bird strikes against aircraft as they took off or landed, especially if the airport was adjacent to coastal sites rather than being offshore.

It would be foolish to suggest that there are solutions to the modern need for expanding airports that would be either cost- free or have no environmental downsides. And of course there are many small residential communities alongside the Thames estuary that would would be unimpressed by the case for a new airport in their neighbourhood.

The idea of a new London airport in the Thames estuary is not new. But nor will it go away. For every rejection of it by advocates of a bigger Heathrow, there have been equally powerful champions of this radical alternative.

One thing is clear. Those who are calling for a third runway at Heathrow must be frank and admit that even if that was built, it would only bring short-term relief. Indeed, on the day that such a new runway was inaugurated there would doubtless be grave warnings from BAA and British Airways that there would soon be an urgent need for a fourth runway, and probably one or two more terminals as well.

I do not criticise them. It is inevitable that the demand for air journeys will expand substantially over the next 30 years especially because of London’s and Britain’s geographical position as the bridge between Europe and North America.

For those reasons the Government and Justine Greening, the Transport Secretary, should announce a comprehensive analysis of the pros and cons of the Thames estuary option, with the study to be completed over the next two years.

I had the doubtful pleasure of being the Transport Secretary from 1990 to 1992. I can understand the conflicting pressures that Greening has to deal with. Londoners should be pleased, and relieved, that it is the MP for Putney who is in charge of that Department. She will have to recommend to the Cabinet decisions that will be to the benefit of the UK as a whole, but at least we can rest assured that the implications for the millions of people who live in London will be fully taken into account. That is not a bad start.

Sir Malcolm Rifkind is MP for Kensington.