A SECRET Gatwick dossier detailing how to win over decision makers for expansion plans was left on a train.

The document, which was sent to a Sunday newspaper, includes plans to draw up “target lists” of key politicians and decision makers who could sway the decision in their favour.

The plans seek to influence the Airports Commission, which will submit its recommendations to government next year as to how the UK can maintain its global airport hub status.

The three leading proposals are a second runway at Gatwick, a third runway at Heathrow or the creation of a new airport in the Thames Estuary.

The secret dossier says Gatwick should target around 100 “gold tier” people with the most influence on the commission.

The plans reveal how Gatwick executives will try to win over gold targets as well as getting onside their close advisors, known as the “silver tier”.

The dossier states that one so-called target, former CIA analyst Dame DeAnne Julius, is backing Gatwick’s case.

The dossier also states the intention to “neutralise the prevailing default bias in favour of Heathrow”.

It mentions a secret noise study aimed at undermining Heathrow’s claim that fewer people would suffer from aircraft noise if a third runway was built there.

Heathrow states the number of people “significantly annoyed” by aircraft noise would drop from 237,350 to between 187,000 and 202,900 due to quieter aircraft and steeper landing approaches.

In the dossier, Gatwick describes the figures as “disingenuous”. It also reveals bosses commissioned the Civil Aviation Authority to model the noise impact of their rival’s potential third runway.

Gatwick’s campaign is overseen by Godric Smith, a former spin doctor to Tony Blair. A Gatwick spokeswoman said: “We want as many people as possible to understand our case. We are playing catch up with Heathrow’s decades of lobbying for a third runway.”