100ml

I used to be completely on board with the 100ml limit on liquids when travelling. But is it all still really necessary? I think we should be told. What I don't understand is that you can take as many items 100ml and under AS LONG AS THEY ALL FIT INTO A TINY PLASTIC BAG. What do you think my chances are of getting a 250g jar of Marmite through Gatwick tomorrow? The UK.gov website clearly states the 100ml limit is for liquids only - Ive got my speech ready about how grams measure mass and mls measure volume. Wish me luck :)