"I understand this is a very difficult situation for many people."

These were among the first words spoken by Colin Matthews from his seat in the massive boardroom of BAA's head office in Bath Road, Harmondsworth.

They were to be repeated several times as the former head of Severn Trent attempted to appease those still reeling from the approval for a £9billion expansion project at the world's busiest airport.

All the campaign groups fighting to disrupt BAA's plans - including a coalition of west London councils known as the 2M Group - say the scheme will have further negative impact on the area's already sky-high air and noise pollution levels.

However, Mr Matthews insists his team and the Government have got their sums right and feels the battle now is to convince the general public.

He said: "I think the signs are there that people are starting to have confidence in us - what we now have to do is work hard to regain the trust of all those who opposed this plan.

"Whether this is through smaller meetings in the local communities or in one big set piece where everyone is invited, it does not matter - the important thing is to talk.

"I am perfectly willing to come down to the affected villages and talk to them face-to-face. They are bound to be cross, I know this. My job is to ensure the negative impacts of the plan are minimised. I realise no amount of compensation can off set the disruption to people's lives.

"It is not just about money. We know people have attachment to churches, schools, houses, etc. No amount of money can remove that concern."

One of the main accusations Mr Matthews and his team face is that the public consultation sent out last year on the expansion plans was a sham. He vigorously denies this and insists everything is being done in the appropriate manner.

He added: "Obviously there are good sides to this decision, and there are bad sides. The important thing now is to balance both sides out, so we get the best deal for everyone."

But not quite everything was gilded in BAA's favour. The Government refused to allow an increase in capacity of the existing runways - a practice known as mixed mode.

The disastrous opening of Terminal 5 last year which led to lost baggage and hundreds of delayed flights, has also raised questions over BAA's ability to operate another terminal.

Mr Matthews insists mistakes will not be repeated. He said: "The new expansion is a way off and in the meantime, we are completely rebuilding Terminal 4 and making many improvements to Terminal 1. We are spending £1bn a year over the next four years. There is an economic crisis gripping the country at the moment, but I think people should draw hope from the fact we are confident enough to invest such sums of money."

BAA is owned by the Spanish firm Ferrovial, and Mr Matthews has already had to complete a complicated refinancing process to reduce the debt since it took over in 2006, including putting Gatwick Airport up for sale.

But the toughest battle lies ahead. Several high-profile demonstrations against a third runway including a protest march and giant NO,as well as a Climate Camp, have already taken place.

Last week Andrew Slaughter,Labour MP for Ealing, Acton and Shepherd's Bush, quit his Government post over the issue, and an unlikely coalition of anti-climate change activists and west Londoners threatened by increased noise, are promising a vigorous direct action campaign.

Mr Matthews insists he is not preparing for a mass invasion of the land to be developed (similar to the Newbury ByPass protests of 1996) but is aware the protests may gain in strength. He said: "People have strong views and a right to express them, but if they wish to fight this plan, I would hope they do it via the proper channels. People have a right to travel unhindered and if people attempt to disrupt the airport obviously we will take action.

We certainly do not underestimate the strength of feeling and the message from the protesters has been heard very clearly."

The vast majority of campaigners are now pinning their hopes on a Conservative victory at the next General Election to halt the plan, as the Tories have vowed not to support a third runway. But whoever is in Downing Street next year,Mr Matthews vows to fight the corner of airport expansion.