In the UK, there are strict security rules on the amount of liquid a passenger can take on an aircraft. Including water, sprays, toothpaste etc. - only 100 ml may be taken on board.
Rules are strictly observed and closely monitored, in the departure process. Even the liquid receptacles have to be displayed separately, in a see through bag - and extracted from suitcases etc.
Gatwick and Heathrow are particularly vigilant, and bottles of expensive liquid substances are often confiscated, or discarded - to allow the boarding to continue.
Most ironically and irrationally - the same procedures are totally ignored in most European airports. You can bring as much liquid on board, as you want!
Recently, in my experience - Madrid, Budapest, Dublin (for example) all had the same disinterest in flying liquids.
And, of course, the disinterest is repeated on your arrival back at Gatwick and Heathrow!