Around 90 airlines use Heathrow, one of the world's busiest airports

Laptops are being removed from cases before X-ray screenings and passengers' belts must be checked after a security review by airport operator BAA.

British Airways is warning that the new checks are leading to delays for passengers of all airlines.

BAA hopes the compulsory measures will reduce disruption by cutting the number of times body scanners are set off.

A BAA spokesman said the latest changes were part of "the ongoing strengthening of security procedures".