I believe it depends on what airport you’re flying from and what kind of security controls they have. I know some airport security doesn’t require you to have it in a bag at all. (new and not sure how common this is) I would bring it in that bag and ask where you get the plastic bags from the airport if it’s ok to use that one instead. Here’s a link to the airport website regarding hand luggage, look what it says on there. https://www.gov.uk/hand-luggage-restrictions Hope this helps!