On a previous flight, I've had a biro taken off me at airport security because it could be used as an offensive weapon to stab a person. When I protested, was told I would not be allowed to go through security to the aircraft.
Didn't stop cabin crew handing out biros on the plane to complete a survey though
At some point, we have to decide what risks we will accept in life
https://www.gov.uk/hand-luggage-restrictions/personal-items