Heathrow airport has warned airlines that passengers could face 12-hour delays next week
when immigration officers go on strike over pensions.
Chief operating officer Norman Boivin said there was a danger of "gridlock". Heathrow operator BAA has been
holding talks with airlines and the UK Border Agency to try to minimise the impact of Wednesday's public sector strike.
PM David Cameron said it was clear there would be an impact at ports and airports but borders would be secure.
"At the very least there will be longer queues and people will have to wait longer at borders," his spokesman