British Airways boss alarmed to find out Heathrow's third runway will flatten his multi-million-pound HQ

Biggest customer of airport only found out offices would be razed after looking at map

Boss of IAG fears his company will effectively have to pay for the demolition of its own headquarters (PA)

The head of British Airways’ parent company was not given any warning the third runway at Heathrow would involve the demolition of his companys’ multi-million-pound offices.

British Airways is the biggest customer at Heathrow and its owner company IAG is responsible for around half of the flights at the airport.

Yet chief executive Willie Walsh only found out his company's HQ would be razed after he looked at a map, he has said.

“We were never actually informed or advised by Heathrow that they intended to knock down our headquarters,” he told The Guardian.

“The first I saw of it was when the Airport Commission report came out and I saw a map and I thought: that looks very close to Waterside.

“Then I discovered it actually went right through Waterside.”

IAG and British Airways are based in a business complex in Harmondsworth that was constructed in 1998 for £200m.

The office space sits in a 115-hectare man-made park and is equipped with its own travel centre, beauty salon, 400-seater auditorium and Waitrose supermarket.

Mr Walsh fears IAG will effectively have to pay for the demolition of its own HQ, since although the properties cleared to make way for the runway will be bought for 25 per cent more than their market value, airlines are likely going to have to pay far more to the Civil Aviation Authority to compensate for the expansion costs.

October's decision to expand the airport at Heathrow has caused uproar among environmental campaigners and residents in the area.

Up to 4,000 residents in the area could lose their homes.

But High Court challenges could yet derail the decision, and the razing of Harmondsworth – along with British Airways' HQ – is unlikely to start before 2020.