As stated in the above link, on the 15th March 2008, at the STWC anti-war demonstration in Trafalgar Square, 4 people were arrested under the Trade Union and Labour Relations (Consolidation) Act 1992 for allegedly encouraging employees (Metropolitan FIT team) from carrying out their awful work. This was seen as a breach of the Trade Union Act as the correct union proceedures had not been followed.
As one arrestee was being booked into the City of London police station, a custody sergeant stated:
"This isn't going to work... Even if they get found guilty of this, it's just going to go to judicial review and we won't be able to use it anymore. They'll only be able to arrest once under this act. We might as well just drop it now."
Despite the fact that the police at the time did not feel it was possible to arrest the 4 for obstruction, the charge has been changed to obstruction of police. It occurs to the author of this article that this leaves the way open for further misinterpretations and abuse of Sec 241 in the future.
Obstruct PC does not have case law behind it to cover this situation, the case law is very much in the Fitwatcher's favour.