A multi-million pound investment in Gatwick will help tighten airport security in the aftermath of the September 11 terrorist attacks.

Part of the £980 million boost announced by airports operator BAA yesterday will be spent on separating in-bound and out-bound passengers as they travel walkways between departure lounges and gates.

The spending programme was announced by BAA chief executive Mike Hodgkinson as part of a ten-year £8.1 billion investment plan at London's three main airports.

A Gatwick spokeswoman said: "Some of the segregation work has been introduced post September 11.

"It is so in-bound passengers don't come into contact with out-bound passengers at all.

"Where people meet at the moment and potentially come into contact we have got secondary search procedures in place.

"There are security staff and metal archway detectors at those points.

"The announcement to do this is the next step on from the development strategy launched in 2000, which set out a blueprint on how airports are going to grow in the next ten years."

It does not take into account any plan to build an extra runway at Gatwick.

Other projects BAA will carry out at Gatwick include extensions to both the north and south terminals, car park improvements and the construction of an extra mini-terminal.

The programme will mean hundreds more jobs in the construction industry but no announcement has been made about whether extra airport jobs will be created.

The BAA investment programme, some of which will need planning permission, assumes air traffic will double in the next 20 years.