the ignigion in the cooker won't turn off even when the nob is turned to th?

First of all turn off the gas supply at the Emergency service cock at the Gas Meter.
The inside of the plastic knob is probably broken or worn,it should just pull off.Do this then turn off the tap with a pair of pliers,do NOT force it,it should turn quite easily.If it doesn`t call Transco and tell them you cannot turn off your gas,they`ll send someone round within an hour(non-chargeable).If it does turn off easily leave it off and order a new tap from the manufacturers or a parts supplier.

Gasman
August 2008