No one loves London's Heathrow airport but it's been there a long time and until now the idea that it should be replaced has not been given much credence. But in a sort of pincer movement the Conservative Party has suddenly launched two initiatives that could seriously affect Heathrow's future.

The first, curiously enough, concerns trains rather than planes. The shadow Transport Secretary, Theresa Villiers, has pledged that a Conservative government would build a high-speed, north-south railway linking Leeds with Heathrow airport and the Channel Tunnel. Where would the money come from?

From not building the projected third runway at Heathrow, that's where -- the thinking being that a rail link of this kind would drastically reduce the number of UK short-haul flights that currently clog-up Heathrow's runway capacity. The second Conservative initiative is Boris Johnson's idea for a completely new Thames airport which came to him late one night at Gatwick when his baggage was delayed by a handlers' strike. It's not a new idea and whether its time has now come depends on a closer study than it has had so far. A huge amount of money would be required for an island site in the Thames with fast connections to all other major transport hubs. There would also be serious questions to be asked about the environmental consequences for what is still a relatively undeveloped area despite its proximity to London.