A conference last week addressed the question of what to do about aviation. This is a very vexed question – we all want to travel and mostly want to fly. But none of us want aircraft overhead or runways gobbling up land. And our most successful airport, Heathrow, has only two runways where most large international airports have at least four. Moreover, Heathrow is to the West of London, which given prevailing winds, means that large aircraft in crowded airspace fly over a densely packed city. You certainly wouldn’t want to start from here.

Forecasts of demand for air travel suggest that it will double, at least, in the next thirty years. Both the globalisation of business and rising incomes worldwide will ensure this. If the UK does not provide for this increase, we will lose out and risk becoming a global backwater. Already we are losing destinations – Heathrow serves less than 200 destinations, while Frankfurt, Schiphol and Paris serve around 220. As new cities join the global economy it will be easier to reach them from other locations than London, while equally the citizens of those places will in turn do business in the places which it is easiest to reach.

Of course, London is a true global city and remains well connected to other such cities – we are not on the edge of a cliff. Nonetheless unless we keep up, decline is inevitable.

The clear need for additional capacity, expressed both by myself and other speakers, does not however generate a clear solution. In the short term, better use of existing capacity, and more flexible use of Heathrow are potential supports. But they do not answer the longer term question. World class cities need world class airports, which are flexible, large, resilient to weather and the inevitable disruptions. Heathrow cannot become such an airport – even the 3rd runway over which there has been such dispute only adds 10 per cent to capacity. It is short, and tucked between existing runways.

A full scale airport therefore needs considerable space. A runway needs to be 3.5 kilometres long and 1.5 kilometres away from the next runway if it is to be used independently to guarantee flexibility. I do not believe that there is anywhere on land where it would be possible to put such an investment without too much damaging disruption to people. The space left is therefore on the sea. This is the solution that Hong Kong has chosen. Runways therefore are not near residents, do not create noise nuisance, and do not displace existing activities. All other options do and especially this is true of the expansion of existing airports.

Of course existing airports have existing infrastructure and access. However, no existing London airports have spare access capacity, so expansion requires significant investment in access wherever it is put. Spreading additional capacity across several airports means that additional access capacity would have to be put in place for several locations, as well as much improved connections between the airports. It is not a cheap alternative to a new location, though it certainly protects existing investors and shareholders.

Over time, business responds to new infrastructure, and Heathrow became the access point for the US software houses and the investments along the M4. However, that is a generation ago – these businesses now do business as much with each other as requiring that US link. Scaling Heathrow back to a less noisy and disruptive activity could still fulfil this role as a business airport connecting to Europe as well as to the US. In turn a new airport could help generate the new investment in new industries as they emerge. Policy and availability is generating investment to the East of London, so it is here that new infrastructure needs to be focused. An airport here can support and exploit these new connections and runways over sea will minimise environmental impacts. It is the one that the UK should look at very seriously.