A few years ago the pilot of a single engine aircraft crossed the city heading to Biggin Hill. He ran out of fuel and attempted to Land an London City. He did not make the airport, but did a perfect forced landing in a small green patch with very little damage to the aircraft.
The pilot was charged with a number of offences including endangerment of persons on the ground Art 64, and of the aircraft Art 63. After some trading, the endangermeant charges were dropped,on condition that the pilot pleaded guilty to an offence under Art 43. Either way he was prosecuted.
Whilst you might not be taken to task for crossing the zone, if it goes wrong, you may well be prosecuted.