Banned Items at LHR include:
Sharp items
This includes knives (with blades over 6cm), razor blades, box cutters, scissors (with blades over 6cm from fulcrum), axes, hatchets, cleavers, ice axes, ice picks, swords, sabres and sharp or pointed martial arts equipment
Heathrow: Hand baggage and liquids | Cabin luggage screening at Heathrow