Tom,
I have bad news for you - best to sit down.
Your kettle has boiled its last water - say goodbye to it and get a new one. Very probably the kettle's element has gone open circuit.
All electric kettles have a temperature trip - it cuts off the power when the water is boiled - the light on your old kettle says that it's working OK.
Condolences
Peccavi
April 2010