This was a hot topic a few years ago when the so-called "journalists" from Daily Mail found out about this possibility http://www.dailymail.co.uk/news/article-2396327/Airport-security-farce-Deadlier-knives-used-9-11-sold-duty-free-taken-London-flight.html Maybe also due to the draconic UK knife laws they saw it as aan extremely dangerous thing.
The Daily Mail article claims (not that I trust this tabloid too much):
- Expert says he would not have been able to board UK flight with the blades
- On U.S. flights all types of blades, even penknives, are banned
According to Wikipedia:
A common regulation for cabin baggage restrictions was introduced on 6 November 2006 in European Union and in Switzerland, Norway and Iceland: ... The recommendation allows for light knives and scissors with blades up to 6 cm but some countries do not accept these either (e.g. nail care items)
@Kuba referenced the UK website which mentions knifes above 6mm to be forbidden. But I would expect to have problems with a small knife on a UK airport in practice too. At least Daily Mail claims so. Remember that "Airport security staff won’t let anything through that they consider dangerous - even if it’s normally allowed in hand luggage." (https://www.gov.uk/hand-luggage-restrictions]https://www.gov.uk/hand-luggage-restrictions)