ignition lights come on in 1998 1.0l corsa without key in ignition and wont?

Hi, my sons car has just started to play up. He stopped for fuel and vehicle wouldnt start apart from a bump start. When he got to work he took key out of ignition and car continued to run. He stalled car to stop it butthe ignition lights remained.on even with key removed. After disconnecting the battery and then reconnecting the ignition light have remained on and car refuses to start. Any ideas gratefully received
Thanks
Paul