A new trial at Heathrow Airport that allows passengers to fast-track the security queue will start on Tuesday.Heathrow is trying to change the travel experience for passengers with a new system that allows people to pre-book security slots through their website.The initiative, called Heathrow Timeslot, will begin on a six-month trial basis and will be available in Terminal 3. The free service gives passengers a designated time and entry point to the security search area and speeds up the process.