The terror threat to the UK has been downgraded from "critical" to "severe".
Home Secretary John Reid said the change was made because an attack was "highly likely" but not "imminent".
The change in the threat level means the ban on taking hand luggage on to flights from the UK has been lifted, although some restrictions remain.
These are the new rules but it looks likely that it will be tomorrow before they will be fully implemented:
Following the Joint Terrorist Analysis Centre's decision to change the UK threat level from Critical to Severe, the following aviation security measures will apply at all UK airports with immediate effect. Following the Joint Terrorist Analysis Centre's decision to change the UK threat level from Critical to Severe, the following aviation security measures will apply at all UK airports with immediate effect.
These arrangements apply to all passengers starting their journey at a UK airport and to those transferring from international flights at a UK airport.
Each passenger is permitted to carry ONE item of cabin baggage through the airport security search point. The dimensions of this item must not exceed: a maximum length of 45 cm, width of 35 cm and depth of 16 cm (17.7"×13.7"×6.2" approx) (including wheels, handles, side pockets etc.). Other bags, such as handbags, may be carried within the single item of cabin baggage. All items carried by passengers will be x-ray screened.
No liquids of any type are permitted through the airport security search point, other than the following items:
Essential medicines in liquid form sufficient and essential for the flight (e.g. diabetic kit), as long as verified as authentic
Baby milk and liquid baby food (the contents of each bottle or jar must be tasted by the accompanying passenger).
NOTE: The definition of liquids includes gels, pastes, lotions, liquid/solid mixtures and the contents of pressurised containers, e.g. toothpaste, hair gel, drinks, soups, syrups, perfume, deodorant, shaving foam, aerosols, etc.
To help their progress through search points, passengers are encouraged not to include items capable of containing liquids (e.g. bottles, flasks, tubes, cans, plastic containers etc.) in their cabin baggage.
All laptops and large electrical items (e.g. large hairdryer) must be removed from the bag and placed in a tray so that such items neither obscure nor are obscured by the bag.
Pushchairs and walking aids are permitted but must be x-ray screened. Wheelchairs are permitted but must be thoroughly searched.
In addition to the above, passengers boarding flights to the USA and items they are carrying, including those acquired after the central screening point, will be subjected to secondary search at the gate. Any liquids discovered will be removed from the passenger.
The Department for Transport will work closely with operators to introduce these new arrangements, seeking to keep disruption to passengers to a minimum. The Department will keep these measures under review.
If passengers have any questions on their travel arrangements or security in place at airports they should contact the airport or their airline.