nonetheless, from midnight tonight, the largest pollution charging zone in the world begins. tom edwards, bbc news. other cities are watching closely to see what happens in london. we re joined now by our transport correspondent, katy austin. many people were hoping there might be a rethink and it might not happen. be a rethink and it might not ha en. , ., , be a rethink and it might not ha en. , . , ., happen. they might have been at the ma or has happen. they might have been at the mayor has stuck happen. they might have been at the mayor has stuck to happen. they might have been at the mayor has stuck to his happen. they might have been at the mayor has stuck to his guns, - mayor has stuck to his guns, insisted that it is a necessary extension to clean up the air and that means that from tomorrow, we are going to have this big function of ulez. i m right on the edge of the current ultra low emission zone, you can see the sign warning drivers they are about to head into it, tomo