750XL
Quite clearly you don't understand UK airport security, they make up the rules as they go along, what might be seen as perfectly innocent cheese & pickle sandwich at one airport would be considered to contain pickle , that is a sauce and therefore a liquid and therefore contraband at another airport.
Getting the average workers lunchbox through security is a minefield and if you protest they will try to take away your airport pass....... no pass no job.
This is one of the reasons airlines supply crew food.